/* ============================================
   AI CALCULATOR — Premium Dark Theme
   ============================================ */

:root {
    /* Colors */
    --bg-primary: #0a0a1a;
    --bg-secondary: #111128;
    --bg-tertiary: #191940;
    --bg-card: rgba(25, 25, 64, 0.6);
    --bg-card-hover: rgba(35, 35, 80, 0.8);
    --bg-glass: rgba(255, 255, 255, 0.03);
    --border-color: rgba(99, 102, 241, 0.15);
    --border-active: rgba(99, 102, 241, 0.4);

    /* Text */
    --text-primary: #e8e8ff;
    --text-secondary: #8b8bbd;
    --text-muted: #5a5a8a;
    --text-accent: #a78bfa;

    /* Accent Colors */
    --accent-primary: #6366f1;
    --accent-secondary: #a855f7;
    --accent-gradient: linear-gradient(135deg, #6366f1, #a855f7, #ec4899);
    --accent-glow: rgba(99, 102, 241, 0.25);
    --accent-cyan: #22d3ee;
    --accent-green: #34d399;
    --accent-amber: #fbbf24;
    --accent-rose: #f43f5e;

    /* Buttons */
    --btn-num-bg: rgba(255, 255, 255, 0.06);
    --btn-num-hover: rgba(255, 255, 255, 0.12);
    --btn-op-bg: rgba(99, 102, 241, 0.15);
    --btn-op-hover: rgba(99, 102, 241, 0.3);
    --btn-fn-bg: rgba(168, 85, 247, 0.12);
    --btn-fn-hover: rgba(168, 85, 247, 0.25);
    --btn-eq-bg: linear-gradient(135deg, #6366f1, #a855f7);
    --btn-eq-hover: linear-gradient(135deg, #7c7ff7, #b86af9);

    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.5);
    --shadow-glow: 0 0 30px rgba(99, 102, 241, 0.15);

    /* Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-2xl: 24px;

    /* Font */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Transitions */
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
}

/* Light theme */
[data-theme="light"] {
    --bg-primary: #f0f0ff;
    --bg-secondary: #e8e8f8;
    --bg-tertiary: #ddddf5;
    --bg-card: rgba(255, 255, 255, 0.7);
    --bg-card-hover: rgba(255, 255, 255, 0.9);
    --bg-glass: rgba(255, 255, 255, 0.5);
    --border-color: rgba(99, 102, 241, 0.2);
    --border-active: rgba(99, 102, 241, 0.5);
    --text-primary: #1a1a3a;
    --text-secondary: #555580;
    --text-muted: #8888aa;
    --text-accent: #7c3aed;
    --btn-num-bg: rgba(0, 0, 0, 0.05);
    --btn-num-hover: rgba(0, 0, 0, 0.1);
    --btn-op-bg: rgba(99, 102, 241, 0.1);
    --btn-op-hover: rgba(99, 102, 241, 0.2);
    --btn-fn-bg: rgba(168, 85, 247, 0.08);
    --btn-fn-hover: rgba(168, 85, 247, 0.18);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.12);
    --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.15);
    --shadow-glow: 0 0 30px rgba(99, 102, 241, 0.1);
}

/* ===================== RESET ===================== */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* Screen reader only — hidden visually but crawlable by search engines & AI */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    position: relative;
}

/* ===================== BACKGROUND CANVAS ===================== */
#bg-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
}

/* ===================== APP CONTAINER ===================== */
.app-container {
    position: relative;
    z-index: 1;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* ===================== HEADER ===================== */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 24px;
    background: rgba(10, 10, 26, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
}

[data-theme="light"] .app-header {
    background: rgba(240, 240, 255, 0.85);
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon svg {
    width: 36px;
    height: 36px;
}

.logo-text {
    display: flex;
    flex-direction: column;
}

.logo-name {
    font-size: 1.1rem;
    font-weight: 800;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.02em;
}

.logo-tagline {
    font-size: 0.65rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-weight: 500;
}

/* Nav */
.main-nav {
    display: flex;
    gap: 4px;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 4px;
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border: none;
    border-radius: var(--radius-lg);
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s var(--ease-out);
    white-space: nowrap;
}

.nav-btn:hover {
    color: var(--text-primary);
    background: var(--btn-num-bg);
}

.nav-btn.active {
    color: #fff;
    background: var(--accent-gradient);
    box-shadow: var(--shadow-glow);
}

.nav-icon {
    font-size: 1rem;
}

.header-right {
    display: flex;
    gap: 8px;
}

.icon-btn {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-glass);
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s var(--ease-out);
}

.icon-btn:hover {
    background: var(--btn-num-hover);
    color: var(--text-primary);
    border-color: var(--border-active);
}

.icon-btn svg {
    width: 18px;
    height: 18px;
}

/* ===================== MAIN CONTENT ===================== */
.main-content {
    flex: 1;
    display: flex;
    align-items: flex-start;
    justify-content: center;
    padding: 24px;
}

.mode-panel {
    display: none;
    width: 100%;
    max-width: 900px;
    animation: fadeInUp 0.4s var(--ease-out);
}

.mode-panel.active {
    display: block;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ===================== CALCULATOR ===================== */
.calculator-layout {
    max-width: 420px;
    margin: 0 auto;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-2xl);
    overflow: hidden;
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.calc-display {
    padding: 28px 24px 20px;
    text-align: right;
    min-height: 140px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    background: linear-gradient(180deg, rgba(99, 102, 241, 0.05) 0%, transparent 100%);
}

.display-history {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 4px;
    min-height: 1.2em;
    font-family: var(--font-mono);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.display-expression {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
    min-height: 1.4em;
    font-family: var(--font-mono);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.display-result {
    font-size: 2.8rem;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--text-primary);
    line-height: 1.1;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    transition: all 0.2s var(--ease-out);
}

.display-result.calculating {
    color: var(--accent-secondary);
}

.calc-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    padding: 12px 16px 20px;
}

.calc-btn {
    height: 62px;
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    font-family: var(--font-primary);
    font-size: 1.25rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s var(--ease-out);
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

.calc-btn::after {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle at center, rgba(255, 255, 255, 0.2) 0%, transparent 70%);
    opacity: 0;
    transition: opacity 0.3s;
}

.calc-btn:active::after {
    opacity: 1;
}

.calc-btn:active {
    transform: scale(0.95);
}

.calc-btn.num {
    background: var(--btn-num-bg);
    color: var(--text-primary);
}

.calc-btn.num:hover {
    background: var(--btn-num-hover);
    border-color: var(--border-color);
}

.calc-btn.op {
    background: var(--btn-op-bg);
    color: var(--accent-primary);
    font-size: 1.4rem;
}

.calc-btn.op:hover {
    background: var(--btn-op-hover);
    border-color: var(--accent-primary);
}

.calc-btn.fn {
    background: var(--btn-fn-bg);
    color: var(--accent-secondary);
}

.calc-btn.fn:hover {
    background: var(--btn-fn-hover);
    border-color: var(--accent-secondary);
}

.calc-btn.equals {
    background: var(--btn-eq-bg);
    color: #fff;
    font-size: 1.5rem;
    border: none;
}

.calc-btn.equals:hover {
    background: var(--btn-eq-hover);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.4);
}

.calc-btn.zero {
    grid-column: span 2;
}

.calc-btn.sci {
    background: rgba(34, 211, 238, 0.08);
    color: var(--accent-cyan);
    font-size: 0.85rem;
    font-weight: 700;
}

.calc-btn.sci:hover {
    background: rgba(34, 211, 238, 0.18);
    border-color: var(--accent-cyan);
}

/* ===================== SCIENTIFIC ===================== */
.scientific-layout {
    max-width: 620px;
    margin: 0 auto;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-2xl);
    overflow: hidden;
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.sci-buttons {
    display: grid;
    grid-template-columns: repeat(6, 1fr);
    gap: 6px;
    padding: 12px 14px 20px;
}

.sci-buttons .calc-btn {
    height: 52px;
    font-size: 0.85rem;
}

.sci-buttons .calc-btn.num {
    font-size: 1.15rem;
}

.sci-buttons .calc-btn.equals {
    grid-column: span 1;
}

.sci-equals {
    grid-column: span 1 !important;
}

/* ===================== CONVERTER ===================== */
.converter-layout {
    display: grid;
    grid-template-columns: 220px 1fr;
    gap: 20px;
    max-width: 850px;
    margin: 0 auto;
}

.converter-categories {
    display: flex;
    flex-direction: column;
    gap: 4px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 12px 8px;
    max-height: calc(100vh - 140px);
    overflow-y: auto;
    box-shadow: var(--shadow-md);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.converter-categories::-webkit-scrollbar {
    width: 4px;
}

.converter-categories::-webkit-scrollbar-thumb {
    background: var(--accent-primary);
    border-radius: 4px;
}

.cat-btn {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 14px;
    border: none;
    border-radius: var(--radius-md);
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.82rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s var(--ease-out);
    white-space: nowrap;
}

.cat-btn:hover {
    background: var(--btn-num-hover);
    color: var(--text-primary);
}

.cat-btn.active {
    background: var(--accent-gradient);
    color: #fff;
    box-shadow: var(--shadow-glow);
}

.cat-icon {
    font-size: 1.1rem;
}

.converter-main {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 28px;
    box-shadow: var(--shadow-md);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.converter-title {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: 24px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.converter-body {
    display: flex;
    flex-direction: column;
    gap: 16px;
    align-items: center;
}

.convert-from,
.convert-to {
    width: 100%;
}

.convert-label {
    display: block;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
    margin-bottom: 8px;
    font-weight: 600;
}

.convert-input-group {
    display: flex;
    gap: 10px;
}

.convert-input {
    flex: 1;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 14px 16px;
    font-family: var(--font-mono);
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--text-primary);
    outline: none;
    transition: all 0.2s var(--ease-out);
}

.convert-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.result-input {
    color: var(--accent-cyan);
    font-weight: 700;
}

.convert-select {
    width: 160px;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 14px 12px;
    font-family: var(--font-primary);
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-primary);
    cursor: pointer;
    outline: none;
    transition: all 0.2s var(--ease-out);
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath d='M6 8L1 3h10z' fill='%238b8bbd'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 32px;
}

.convert-select option {
    background: #1a1a40;
    color: #e8e8ff;
    padding: 8px 12px;
}

[data-theme="light"] .convert-select {
    background-color: #fff;
}

[data-theme="light"] .convert-select option {
    background: #fff;
    color: #1a1a3a;
}

.convert-select:focus {
    border-color: var(--accent-primary);
}

.swap-btn {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: 2px solid var(--border-active);
    background: var(--bg-card);
    color: var(--accent-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s var(--ease-spring);
    flex-shrink: 0;
}

.swap-btn:hover {
    background: var(--accent-primary);
    color: #fff;
    transform: rotate(180deg);
}

.swap-btn svg {
    width: 20px;
    height: 20px;
}

.conversion-formula {
    margin-top: 20px;
    padding: 14px 18px;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-secondary);
    text-align: center;
}

.quick-conversions {
    margin-top: 20px;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
}

.quick-conv-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 14px;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.8rem;
    transition: all 0.2s;
}

.quick-conv-item:hover {
    border-color: var(--border-active);
    background: var(--bg-card-hover);
}

.quick-conv-unit {
    color: var(--text-muted);
    font-weight: 500;
}

.quick-conv-value {
    color: var(--accent-cyan);
    font-family: var(--font-mono);
    font-weight: 600;
}

/* ===================== FINANCIAL ===================== */
.financial-layout,
.health-layout {
    max-width: 700px;
    margin: 0 auto;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-2xl);
    overflow: hidden;
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.fin-tabs {
    display: flex;
    gap: 2px;
    padding: 12px 12px 0;
    overflow-x: auto;
    flex-wrap: wrap;
}

.fin-tab {
    padding: 10px 16px;
    border: none;
    border-radius: var(--radius-md) var(--radius-md) 0 0;
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.82rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    white-space: nowrap;
}

.fin-tab:hover {
    background: var(--btn-num-bg);
    color: var(--text-primary);
}

.fin-tab.active {
    background: var(--accent-gradient);
    color: #fff;
}

.fin-content {
    padding: 24px;
}

.fin-panel {
    display: none;
    animation: fadeInUp 0.3s var(--ease-out);
}

.fin-panel.active {
    display: block;
}

.fin-form {
    display: grid;
    gap: 16px;
    margin-bottom: 24px;
}

.fin-field label {
    display: block;
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin-bottom: 6px;
    font-weight: 600;
}

.fin-input-wrap {
    display: flex;
    align-items: center;
    gap: 0;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    transition: all 0.2s;
}

.fin-input-wrap:focus-within {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.fin-prefix {
    padding: 0 4px 0 14px;
    color: var(--text-muted);
    font-weight: 600;
    font-size: 1rem;
}

.fin-input-wrap .fin-input {
    border: none;
    background: transparent;
    box-shadow: none;
}

.fin-input-wrap .fin-input:focus {
    box-shadow: none;
}

.fin-input {
    width: 100%;
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 12px 14px;
    font-family: var(--font-primary);
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-primary);
    outline: none;
    transition: all 0.2s;
}

.fin-input:focus {
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

select.fin-input {
    cursor: pointer;
    appearance: none;
    background-color: var(--bg-tertiary);
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath d='M6 8L1 3h10z' fill='%238b8bbd'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 32px;
}

select.fin-input option {
    background: #1a1a40;
    color: #e8e8ff;
    padding: 8px 12px;
    font-size: 0.9rem;
}

select.fin-input option:hover,
select.fin-input option:checked {
    background: #2d2d6b;
    color: #fff;
}

[data-theme="light"] select.fin-input {
    background-color: #fff;
}

[data-theme="light"] select.fin-input option {
    background: #fff;
    color: #1a1a3a;
}

[data-theme="light"] select.fin-input option:hover,
[data-theme="light"] select.fin-input option:checked {
    background: #e8e8f8;
    color: #1a1a3a;
}

.fin-calc-btn {
    width: 100%;
    padding: 14px;
    border: none;
    border-radius: var(--radius-md);
    background: var(--accent-gradient);
    color: #fff;
    font-family: var(--font-primary);
    font-size: 0.95rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.3s var(--ease-out);
    letter-spacing: 0.02em;
}

.fin-calc-btn:hover {
    box-shadow: 0 0 25px rgba(99, 102, 241, 0.4);
    transform: translateY(-1px);
}

.fin-calc-btn:active {
    transform: translateY(0) scale(0.98);
}

.fin-results {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: 12px;
    margin-bottom: 20px;
}

.fin-result-card {
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 16px;
    display: flex;
    flex-direction: column;
    gap: 6px;
    transition: all 0.3s;
}

.fin-result-card:hover {
    border-color: var(--border-active);
    box-shadow: var(--shadow-glow);
}

.fin-result-label {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
    font-weight: 600;
}

.fin-result-value {
    font-size: 1.3rem;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--accent-cyan);
}

.fin-chart {
    width: 100%;
    height: 200px;
    margin-top: 10px;
    border-radius: var(--radius-md);
}

/* Tip presets */
.tip-presets {
    display: flex;
    gap: 6px;
    margin-top: 8px;
}

.tip-preset {
    padding: 6px 14px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.78rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.tip-preset:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
    background: var(--btn-op-bg);
}

/* ===================== HEALTH — BMI SCALE ===================== */
.bmi-card {
    align-items: center;
}

.bmi-value {
    font-size: 2.5rem !important;
}

.bmi-category {
    font-size: 0.9rem;
    font-weight: 600;
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    margin-top: 4px;
}

.bmi-scale {
    margin-top: 20px;
    position: relative;
}

.bmi-bar {
    display: flex;
    border-radius: var(--radius-md);
    overflow: hidden;
}

.bmi-section {
    flex: 1;
    padding: 12px 8px;
    text-align: center;
    font-size: 0.7rem;
    font-weight: 600;
    line-height: 1.3;
}

.bmi-section.underweight {
    background: rgba(34, 211, 238, 0.2);
    color: var(--accent-cyan);
}

.bmi-section.normal {
    background: rgba(52, 211, 153, 0.2);
    color: var(--accent-green);
}

.bmi-section.overweight {
    background: rgba(251, 191, 36, 0.2);
    color: var(--accent-amber);
}

.bmi-section.obese {
    background: rgba(244, 63, 94, 0.2);
    color: var(--accent-rose);
}

.bmi-indicator {
    position: absolute;
    bottom: -8px;
    width: 3px;
    height: calc(100% + 12px);
    background: var(--text-primary);
    border-radius: 2px;
    transition: left 0.5s var(--ease-spring);
    display: none;
}

/* ===================== PROGRAMMER ===================== */
.programmer-layout {
    max-width: 500px;
    margin: 0 auto;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-2xl);
    overflow: hidden;
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.prog-display {
    padding: 24px;
}

.prog-bases {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.prog-base-row {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    background: var(--bg-glass);
    border: 1px solid transparent;
    transition: all 0.2s;
}

.prog-base-row:hover {
    border-color: var(--border-color);
}

.prog-base-label {
    width: 40px;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
}

.prog-base-value {
    flex: 1;
    font-family: var(--font-mono);
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-align: right;
    word-break: break-all;
}

.prog-base-value.active {
    color: var(--accent-cyan);
    font-size: 1.3rem;
}

.prog-base-selector {
    display: flex;
    gap: 4px;
    padding: 0 16px 12px;
}

.prog-base-btn {
    flex: 1;
    padding: 8px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s;
}

.prog-base-btn.active {
    background: var(--accent-gradient);
    color: #fff;
    border-color: transparent;
}

.prog-base-btn:hover:not(.active) {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}

.prog-buttons {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 6px;
    padding: 8px 14px 20px;
}

.prog-buttons .calc-btn {
    height: 50px;
    font-size: 0.9rem;
}

.prog-hex-btn {
    background: rgba(168, 85, 247, 0.1) !important;
    color: var(--accent-secondary) !important;
}

.prog-hex-btn:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

/* ===================== AI CHAT ===================== */
.ai-fab {
    position: fixed;
    bottom: 24px;
    right: 24px;
    width: 56px;
    height: 56px;
    border-radius: 50%;
    border: none;
    background: var(--accent-gradient);
    color: #fff;
    cursor: pointer;
    box-shadow: var(--shadow-md), 0 0 30px rgba(99, 102, 241, 0.3);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 200;
    transition: all 0.3s var(--ease-spring);
}

.ai-fab:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-lg), 0 0 50px rgba(99, 102, 241, 0.5);
}

.ai-fab svg {
    width: 24px;
    height: 24px;
}

.ai-chat-panel {
    position: fixed;
    bottom: 90px;
    right: 24px;
    width: 380px;
    max-height: 520px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    z-index: 200;
    display: none;
    flex-direction: column;
    overflow: hidden;
    animation: slideUp 0.3s var(--ease-spring);
}

.ai-chat-panel.open {
    display: flex;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.95);
    }

    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.ai-chat-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 18px;
    background: var(--accent-gradient);
    color: #fff;
}

.ai-chat-title {
    display: flex;
    align-items: center;
    gap: 8px;
    font-weight: 700;
    font-size: 0.9rem;
}

.ai-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--accent-green);
    animation: pulse 2s infinite;
}

@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.4;
    }
}

.ai-chat-close {
    background: none;
    border: none;
    color: #fff;
    font-size: 1.1rem;
    cursor: pointer;
    opacity: 0.7;
    transition: opacity 0.2s;
}

.ai-chat-close:hover {
    opacity: 1;
}

.ai-chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 16px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    max-height: 360px;
}

.ai-message {
    max-width: 85%;
    animation: fadeInUp 0.3s var(--ease-out);
}

.ai-message.bot {
    align-self: flex-start;
}

.ai-message.user {
    align-self: flex-end;
}

.ai-message-content {
    padding: 12px 16px;
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    line-height: 1.5;
}

.ai-message.bot .ai-message-content {
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}

.ai-message.user .ai-message-content {
    background: var(--accent-gradient);
    color: #fff;
}

.ai-chat-input-wrap {
    display: flex;
    gap: 8px;
    padding: 12px 16px;
    border-top: 1px solid var(--border-color);
}

.ai-chat-input {
    flex: 1;
    background: var(--bg-glass);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 10px 14px;
    font-family: var(--font-primary);
    font-size: 0.85rem;
    color: var(--text-primary);
    outline: none;
}

.ai-chat-input:focus {
    border-color: var(--accent-primary);
}

.ai-chat-send {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    border: none;
    background: var(--accent-gradient);
    color: #fff;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
    flex-shrink: 0;
}

.ai-chat-send:hover {
    transform: scale(1.05);
}

.ai-chat-send svg {
    width: 16px;
    height: 16px;
}

/* ===================== HISTORY PANEL ===================== */
.history-panel {
    position: fixed;
    top: 70px;
    right: -400px;
    width: 360px;
    max-height: calc(100vh - 90px);
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl) 0 0 var(--radius-xl);
    box-shadow: var(--shadow-lg);
    z-index: 150;
    display: flex;
    flex-direction: column;
    transition: right 0.4s var(--ease-out);
    overflow: hidden;
}

.history-panel.open {
    right: 0;
}

.history-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 18px;
    border-bottom: 1px solid var(--border-color);
}

.history-header h3 {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
}

.history-clear {
    border: none;
    background: none;
    color: var(--accent-rose);
    font-family: var(--font-primary);
    font-size: 0.78rem;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.2s;
}

.history-clear:hover {
    opacity: 0.7;
}

.history-list {
    flex: 1;
    overflow-y: auto;
    padding: 12px;
}

.history-empty {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-muted);
    font-size: 0.85rem;
}

.history-item {
    padding: 12px 14px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border-color);
    margin-bottom: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.history-item:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-active);
}

.history-expr {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

.history-result {
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--accent-cyan);
}

.history-time {
    font-size: 0.65rem;
    color: var(--text-muted);
    margin-top: 4px;
}

/* ===================== ENGINEERING ===================== */
/* Hero section */
.eng-hero {
    position: relative;
    padding: 32px 28px 28px;
    margin-bottom: 24px;
    border-radius: var(--radius-2xl);
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.12), rgba(168, 85, 247, 0.08), rgba(236, 72, 153, 0.06));
    border: 1px solid rgba(99, 102, 241, 0.2);
    overflow: hidden;
    animation: heroFadeIn 0.8s var(--ease-out) forwards;
}

.eng-hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -20%;
    width: 400px;
    height: 400px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.08), transparent 70%);
    pointer-events: none;
    animation: heroGlow 6s ease-in-out infinite alternate;
}

.eng-hero::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -10%;
    width: 300px;
    height: 300px;
    border-radius: 50%;
    background: radial-gradient(circle, rgba(168, 85, 247, 0.06), transparent 70%);
    pointer-events: none;
    animation: heroGlow 8s ease-in-out infinite alternate-reverse;
}

@keyframes heroFadeIn {
    from {
        opacity: 0;
        transform: translateY(16px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes heroGlow {
    from {
        transform: scale(1);
        opacity: 0.6;
    }

    to {
        transform: scale(1.3);
        opacity: 1;
    }
}

.eng-hero-content {
    position: relative;
    z-index: 1;
}

.eng-hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 5px 14px;
    background: rgba(99, 102, 241, 0.15);
    border: 1px solid rgba(99, 102, 241, 0.3);
    border-radius: 20px;
    color: var(--accent-primary);
    font-size: 0.72rem;
    font-weight: 700;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    margin-bottom: 14px;
    animation: heroFadeIn 0.8s var(--ease-out) 0.1s both;
}

.eng-hero-title {
    font-size: 2.2rem;
    font-weight: 900;
    color: var(--text-primary);
    line-height: 1.15;
    letter-spacing: -0.5px;
    margin-bottom: 10px;
    animation: heroFadeIn 0.8s var(--ease-out) 0.15s both;
}

.eng-hero-accent {
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.eng-hero-subtitle {
    font-size: 0.88rem;
    color: var(--text-secondary);
    line-height: 1.6;
    max-width: 620px;
    margin-bottom: 22px;
    animation: heroFadeIn 0.8s var(--ease-out) 0.2s both;
}

.eng-hero-stats {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    animation: heroFadeIn 0.8s var(--ease-out) 0.3s both;
}

.eng-hero-stat {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
    padding: 12px 20px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    min-width: 100px;
    transition: all 0.3s var(--ease-out);
}

.eng-hero-stat:hover {
    border-color: var(--accent-primary);
    background: rgba(99, 102, 241, 0.08);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.12);
}

.eng-hero-stat-num {
    font-size: 1.6rem;
    font-weight: 800;
    color: var(--accent-cyan);
    font-family: var(--font-mono);
}

.eng-hero-stat-label {
    font-size: 0.68rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.8px;
}

.engineering-layout {
    max-width: 900px;
    margin: 0 auto;
}

.eng-discipline-tabs {
    display: flex;
    gap: 6px;
    padding: 4px;
    overflow-x: auto;
    scrollbar-width: none;
    -ms-overflow-style: none;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    margin-bottom: 20px;
}

.eng-discipline-tabs::-webkit-scrollbar {
    display: none;
}

.eng-disc-tab {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 10px 16px;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s var(--ease-out);
    white-space: nowrap;
    flex-shrink: 0;
}

.eng-disc-tab:hover {
    background: var(--bg-glass);
    color: var(--text-primary);
    border-color: var(--border-color);
}

.eng-disc-tab.active {
    background: var(--accent-gradient);
    color: #fff;
    border-color: transparent;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
}

.eng-disc-icon {
    font-size: 1.1rem;
}

.eng-disc-name {
    font-size: 0.8rem;
}

.eng-body {
    min-height: 300px;
}

/* Calculator Card Grid */
.eng-calc-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 14px;
    animation: fadeInUp 0.4s var(--ease-out);
}

.eng-calc-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 20px;
    cursor: pointer;
    transition: all 0.3s var(--ease-out);
    text-align: center;
    position: relative;
    overflow: hidden;
}

.eng-calc-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--accent-gradient);
    opacity: 0;
    transition: opacity 0.3s;
}

.eng-calc-card:hover {
    border-color: var(--border-active);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
}

.eng-calc-card:hover::before {
    opacity: 1;
}

.eng-calc-card:active {
    transform: translateY(-2px) scale(0.98);
}

.eng-calc-card-icon {
    font-size: 2rem;
    margin-bottom: 10px;
    opacity: 0.9;
}

.eng-calc-card-name {
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.eng-calc-card-desc {
    font-size: 0.72rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
}

/* Detail Panel */
.eng-calc-detail {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: 24px;
    animation: fadeInUp 0.35s var(--ease-out);
}

.eng-back-btn {
    border: none;
    background: none;
    color: var(--accent-primary);
    font-family: var(--font-primary);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    padding: 6px 0;
    margin-bottom: 12px;
    transition: color 0.2s;
    display: flex;
    align-items: center;
    gap: 4px;
}

.eng-back-btn:hover {
    color: var(--accent-secondary);
}

.eng-detail-title {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.eng-detail-desc {
    font-size: 0.85rem;
    color: var(--text-muted);
    font-family: var(--font-mono);
    margin-bottom: 20px;
}

.eng-detail-form {
    display: grid;
    gap: 14px;
    margin-bottom: 20px;
}

/* Export bar */
.eng-export-bar {
    grid-column: 1 / -1;
    display: flex;
    gap: 10px;
    padding: 10px 0;
    margin-bottom: 6px;
    border-bottom: 1px solid var(--border-color);
}

.eng-export-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s ease;
    font-family: inherit;
}

.eng-export-btn:hover {
    border-color: var(--accent-primary);
    color: var(--text-primary);
    background: rgba(99, 102, 241, 0.1);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.15);
}

.eng-export-btn:active {
    transform: translateY(0);
}

.eng-export-pdf:hover {
    border-color: var(--accent-cyan);
    background: rgba(34, 211, 238, 0.1);
    box-shadow: 0 4px 12px rgba(34, 211, 238, 0.15);
}

.eng-export-copy:hover {
    border-color: var(--accent-green);
    background: rgba(52, 211, 153, 0.1);
    box-shadow: 0 4px 12px rgba(52, 211, 153, 0.15);
}

.eng-export-copied {
    border-color: var(--accent-green) !important;
    color: var(--accent-green) !important;
    background: rgba(52, 211, 153, 0.15) !important;
}

.eng-export-btn svg {
    flex-shrink: 0;
}

/* ===================== RESPONSIVE ===================== */

/* --- Large Tablets / Small Laptops --- */
@media (max-width: 1200px) {
    .mode-panel {
        max-width: 100%;
    }

    .converter-layout {
        max-width: 100%;
    }

    .financial-layout,
    .health-layout {
        max-width: 100%;
    }

    .engineering-layout {
        max-width: 100%;
    }
}

/* --- Tablets (landscape) --- */
@media (max-width: 900px) {
    .converter-layout {
        grid-template-columns: 1fr;
    }

    .converter-categories {
        flex-direction: row;
        flex-wrap: wrap;
        max-height: none;
        overflow-x: auto;
        justify-content: center;
    }

    .cat-btn {
        padding: 8px 12px;
        font-size: 0.75rem;
    }

    .eng-discipline-tabs {
        gap: 4px;
        padding: 3px;
    }

    .quick-conversions {
        grid-template-columns: repeat(2, 1fr);
    }

    .fin-results {
        grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    }
}

/* --- Tablets (portrait) / Small Screens --- */
@media (max-width: 768px) {
    .app-header {
        padding: 10px 12px;
        flex-wrap: wrap;
        gap: 8px;
    }

    .header-left {
        order: 0;
    }

    .header-right {
        order: 1;
    }

    .header-center {
        order: 2;
        width: 100%;
    }

    .main-nav {
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        scrollbar-width: none;
        justify-content: flex-start;
        padding: 3px;
        gap: 2px;
    }

    .main-nav::-webkit-scrollbar {
        display: none;
    }

    .nav-btn {
        padding: 8px 14px;
        font-size: 0.72rem;
    }

    .nav-label {
        display: none;
    }

    .nav-icon {
        font-size: 1.2rem;
    }

    .main-content {
        padding: 12px;
    }

    .calculator-layout,
    .scientific-layout,
    .financial-layout,
    .health-layout,
    .programmer-layout,
    .engineering-layout {
        border-radius: var(--radius-xl);
    }

    /* Calculator */
    .calc-display {
        padding: 20px 16px 16px;
        min-height: 110px;
    }

    .display-result {
        font-size: 2.2rem;
    }

    .calc-buttons {
        gap: 6px;
        padding: 8px 10px 14px;
    }

    .calc-btn {
        height: 54px;
        font-size: 1.1rem;
        border-radius: var(--radius-sm);
    }

    /* Converter */
    .converter-main {
        padding: 18px;
    }

    .convert-input-group {
        flex-direction: column;
    }

    .convert-select {
        width: 100%;
    }

    .conversion-formula {
        font-size: 0.78rem;
        padding: 10px 14px;
    }

    .quick-conversions {
        grid-template-columns: 1fr;
    }

    /* Scientific */
    .sci-buttons {
        grid-template-columns: repeat(5, 1fr);
        gap: 5px;
        padding: 10px 10px 16px;
    }

    .sci-buttons .calc-btn {
        height: 48px;
        font-size: 0.78rem;
    }

    /* Financial / Health */
    .fin-tabs {
        padding: 8px 8px 0;
    }

    .fin-tab {
        padding: 8px 12px;
        font-size: 0.75rem;
    }

    .fin-content {
        padding: 16px;
    }

    .fin-results {
        grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
        gap: 8px;
    }

    .fin-result-value {
        font-size: 1.1rem;
    }

    .fin-result-card {
        padding: 12px;
    }

    /* Programmer */
    .programmer-layout {
        max-width: 100%;
    }

    .prog-display {
        padding: 16px;
    }

    .prog-base-value {
        font-size: 0.85rem;
    }

    .prog-buttons {
        gap: 5px;
        padding: 8px 10px 14px;
    }

    /* Engineering */
    .eng-hero {
        padding: 22px 18px 20px;
        margin-bottom: 16px;
    }

    .eng-hero-title {
        font-size: 1.5rem;
    }

    .eng-hero-subtitle {
        font-size: 0.8rem;
    }

    .eng-hero-stats {
        gap: 6px;
    }

    .eng-hero-stat {
        padding: 8px 14px;
        min-width: 80px;
        flex: 1;
    }

    .eng-hero-stat-num {
        font-size: 1.2rem;
    }

    .eng-calc-grid {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
        gap: 10px;
    }

    .eng-disc-tab {
        padding: 8px 12px;
    }

    .eng-disc-name {
        display: none;
    }

    .eng-calc-detail {
        padding: 16px;
    }

    .eng-detail-title {
        font-size: 1.15rem;
    }

    .eng-export-btn {
        padding: 7px 12px;
        font-size: 0.75rem;
    }

    /* AI Chat */
    .ai-chat-panel {
        width: calc(100% - 20px);
        right: 10px;
        bottom: 80px;
    }

    .ai-fab {
        width: 48px;
        height: 48px;
    }

    /* History */
    .history-panel {
        width: 100%;
    }
}

/* --- Mobile Phones --- */
@media (max-width: 480px) {
    .logo-text {
        display: none;
    }

    .main-content {
        padding: 8px;
    }

    .nav-btn {
        padding: 6px 10px;
    }

    .nav-icon {
        font-size: 1.1rem;
    }

    /* Calculator */
    .calc-display {
        padding: 16px 12px 12px;
        min-height: 90px;
    }

    .display-result {
        font-size: 1.8rem;
    }

    .display-expression {
        font-size: 0.85rem;
    }

    .calc-buttons {
        gap: 4px;
        padding: 6px 8px 10px;
    }

    .calc-btn {
        height: 48px;
        font-size: 1rem;
        border-radius: 6px;
    }

    /* Scientific */
    .sci-buttons {
        grid-template-columns: repeat(4, 1fr);
        gap: 4px;
        padding: 8px 8px 12px;
    }

    .sci-buttons .calc-btn {
        height: 44px;
        font-size: 0.72rem;
    }

    /* Converter */
    .converter-main {
        padding: 14px;
    }

    .convert-input {
        padding: 10px 12px;
        font-size: 0.85rem;
    }

    .convert-select {
        padding: 10px 12px;
        font-size: 0.85rem;
    }

    .swap-btn {
        width: 38px;
        height: 38px;
    }

    .cat-btn {
        padding: 6px 10px;
        font-size: 0.7rem;
        gap: 6px;
    }

    .cat-icon {
        font-size: 0.95rem;
    }

    .quick-conv-item {
        padding: 8px 10px;
        font-size: 0.72rem;
    }

    /* Financial / Health */
    .fin-tab {
        padding: 6px 10px;
        font-size: 0.7rem;
    }

    .fin-content {
        padding: 12px;
    }

    .fin-input {
        padding: 10px 12px;
        font-size: 0.85rem;
    }

    .fin-calc-btn {
        padding: 12px;
        font-size: 0.85rem;
    }

    .fin-results {
        grid-template-columns: 1fr 1fr;
        gap: 6px;
    }

    .fin-result-card {
        padding: 10px;
    }

    .fin-result-label {
        font-size: 0.65rem;
    }

    .fin-result-value {
        font-size: 1rem;
    }

    .bmi-scale {
        flex-wrap: wrap;
    }

    .bmi-section {
        font-size: 0.6rem;
    }

    /* Programmer */
    .prog-display {
        padding: 12px;
    }

    .prog-base-row {
        padding: 6px 10px;
        gap: 8px;
    }

    .prog-base-label {
        font-size: 0.6rem;
    }

    .prog-base-value {
        font-size: 0.8rem;
    }

    .prog-base-btn {
        padding: 6px 10px;
        font-size: 0.7rem;
    }

    .prog-buttons {
        grid-template-columns: repeat(5, 1fr);
        gap: 4px;
        padding: 6px 8px 10px;
    }

    .prog-buttons .calc-btn {
        height: 42px;
        font-size: 0.78rem;
    }

    /* Engineering */
    .eng-hero {
        padding: 18px 14px 16px;
        margin-bottom: 12px;
        border-radius: var(--radius-xl);
    }

    .eng-hero-title {
        font-size: 1.3rem;
        letter-spacing: -0.3px;
    }

    .eng-hero-subtitle {
        font-size: 0.75rem;
        margin-bottom: 16px;
        line-height: 1.5;
    }

    .eng-hero-stats {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 6px;
    }

    .eng-hero-stat {
        padding: 8px 10px;
        min-width: unset;
    }

    .eng-hero-stat-num {
        font-size: 1.1rem;
    }

    .eng-hero-stat-label {
        font-size: 0.6rem;
    }

    .eng-calc-grid {
        grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
        gap: 8px;
    }

    .eng-calc-card {
        padding: 14px;
    }

    .eng-calc-card-icon {
        font-size: 1.6rem;
        margin-bottom: 6px;
    }

    .eng-calc-card-name {
        font-size: 0.8rem;
    }

    .eng-calc-card-desc {
        font-size: 0.65rem;
    }

    .eng-disc-tab {
        padding: 6px 10px;
        font-size: 0.72rem;
    }

    .eng-calc-detail {
        padding: 12px;
    }

    .eng-detail-title {
        font-size: 1.05rem;
    }

    .eng-detail-desc {
        font-size: 0.75rem;
        margin-bottom: 14px;
    }

    .eng-export-bar {
        flex-direction: column;
        gap: 6px;
    }

    .eng-export-btn {
        justify-content: center;
        padding: 8px 14px;
        font-size: 0.75rem;
    }

    /* AI Chat */
    .ai-chat-panel {
        width: calc(100% - 16px);
        right: 8px;
        bottom: 70px;
        max-height: 60vh;
    }

    .ai-chat-input {
        font-size: 0.85rem;
    }

    .ai-fab {
        width: 44px;
        height: 44px;
        bottom: 16px;
        right: 12px;
    }

    .ai-fab svg {
        width: 20px;
        height: 20px;
    }

    /* History */
    .history-panel {
        width: 100%;
    }

    .history-result {
        font-size: 0.95rem;
    }
}

/* --- Small Phones (320-360px) --- */
@media (max-width: 360px) {
    .app-header {
        padding: 8px 8px;
        gap: 6px;
    }

    .logo-icon svg {
        width: 28px;
        height: 28px;
    }

    .icon-btn {
        width: 34px;
        height: 34px;
    }

    .icon-btn svg {
        width: 15px;
        height: 15px;
    }

    .nav-btn {
        padding: 5px 8px;
    }

    .nav-icon {
        font-size: 1rem;
    }

    .main-content {
        padding: 6px;
    }

    /* Calculator */
    .calc-btn {
        height: 42px;
        font-size: 0.9rem;
    }

    .display-result {
        font-size: 1.5rem;
    }

    /* Engineering */
    .eng-hero {
        padding: 14px 12px;
    }

    .eng-hero-badge {
        display: none;
    }

    .eng-hero-title {
        font-size: 1.15rem;
    }

    .eng-hero-subtitle {
        font-size: 0.7rem;
    }

    .eng-hero-stats {
        grid-template-columns: 1fr 1fr;
    }

    .eng-hero-stat-num {
        font-size: 1rem;
    }

    .eng-calc-grid {
        grid-template-columns: 1fr 1fr;
        gap: 6px;
    }

    .eng-calc-card {
        padding: 10px;
    }

    .eng-calc-card-icon {
        font-size: 1.3rem;
        margin-bottom: 4px;
    }

    .eng-calc-card-name {
        font-size: 0.72rem;
    }

    .eng-calc-card-desc {
        display: none;
    }

    /* Financial */
    .fin-results {
        grid-template-columns: 1fr;
    }

    .fin-tab {
        padding: 5px 8px;
        font-size: 0.65rem;
    }

    /* Programmer */
    .prog-buttons {
        grid-template-columns: repeat(4, 1fr);
    }

    .prog-buttons .calc-btn {
        height: 38px;
        font-size: 0.7rem;
    }

    .prog-base-btn {
        padding: 5px 8px;
        font-size: 0.65rem;
    }

    /* Scientific */
    .sci-buttons {
        grid-template-columns: repeat(4, 1fr);
    }

    .sci-buttons .calc-btn {
        height: 40px;
        font-size: 0.68rem;
    }

    /* Converter */
    .converter-main {
        padding: 10px;
    }

    .cat-btn {
        padding: 5px 8px;
        font-size: 0.65rem;
    }
}

/* --- Landscape phone --- */
@media (max-height: 500px) and (orientation: landscape) {
    .app-header {
        padding: 6px 12px;
    }

    .main-content {
        padding: 6px 12px;
    }

    .calc-display {
        min-height: 70px;
        padding: 10px 14px;
    }

    .display-result {
        font-size: 1.6rem;
    }

    .calc-btn {
        height: 40px;
    }

    .eng-hero {
        padding: 14px 20px;
        margin-bottom: 10px;
    }

    .eng-hero-title {
        font-size: 1.3rem;
        margin-bottom: 4px;
    }

    .eng-hero-subtitle {
        display: none;
    }

    .eng-hero-stats {
        gap: 6px;
    }

    .eng-hero-stat {
        padding: 6px 12px;
    }

    .fin-content {
        padding: 12px;
    }

    .ai-chat-panel {
        max-height: 70vh;
    }
}

/* ===================== SCROLLBAR ===================== */
::-webkit-scrollbar {
    width: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: rgba(99, 102, 241, 0.3);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(99, 102, 241, 0.5);
}

/* Number input arrows removal */
input[type=number]::-webkit-inner-spin-button,
input[type=number]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

input[type=number] {
    -moz-appearance: textfield;
    appearance: textfield;
}

/* Selection */
::selection {
    background: rgba(99, 102, 241, 0.3);
    color: var(--text-primary);
}