/* ===== CSS Custom Properties / Design Tokens ===== */
:root {
    --bg-primary: #09090b;
    --bg-secondary: #0f0f13;
    --bg-tertiary: #16161d;
    --bg-card: rgba(22, 22, 30, 0.7);
    --bg-card-hover: rgba(30, 30, 42, 0.8);
    --bg-glass: rgba(255, 255, 255, 0.03);
    --bg-glass-hover: rgba(255, 255, 255, 0.06);
    --text-primary: #ffffff;
    --text-secondary: #d7d7df;
    --text-tertiary: #b8bac7;
    --text-muted: #9ca3af;
    --accent-violet: #a78bfa;
    --accent-pink: #f472b6;
    --accent-orange: #fb923c;
    --accent-cyan: #67e8f9;
    --accent-green: #4ade80;
    --accent-gradient: linear-gradient(135deg, #a78bfa 0%, #f472b6 50%, #fb923c 100%);
    --accent-gradient-subtle: linear-gradient(135deg, rgba(167,139,250,0.15) 0%, rgba(244,114,182,0.15) 50%, rgba(251,146,60,0.08) 100%);
    --border-subtle: rgba(255, 255, 255, 0.06);
    --border-medium: rgba(255, 255, 255, 0.1);
    --border-accent: rgba(167, 139, 250, 0.3);
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.5);
    --shadow-xl: 0 16px 64px rgba(0,0,0,0.6);
    --shadow-glow: 0 0 40px rgba(167,139,250,0.15);
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    --space-4xl: 6rem;
    --radius-sm: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.25rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-display: 'Playfair Display', Georgia, serif;
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
    --duration-fast: 150ms;
    --duration-normal: 300ms;
    --duration-slow: 500ms;
}

/* ===== Reset ===== */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; font-size: 17px; }
body { font-family: var(--font-sans); background-color: var(--bg-primary); color: var(--text-primary); line-height: 1.68; overflow-x: hidden; position: relative; }

/* ===== Ambient Orbs ===== */
.ambient-orb { position: fixed; border-radius: 50%; filter: blur(120px); pointer-events: none; z-index: 0; opacity: 0.5; }
.orb-1 { width: 600px; height: 600px; background: radial-gradient(circle, rgba(167,139,250,0.12) 0%, transparent 70%); top: -200px; right: -200px; animation: orbFloat1 20s ease-in-out infinite; }
.orb-2 { width: 500px; height: 500px; background: radial-gradient(circle, rgba(244,114,182,0.08) 0%, transparent 70%); bottom: 20%; left: -150px; animation: orbFloat2 25s ease-in-out infinite; }
.orb-3 { width: 400px; height: 400px; background: radial-gradient(circle, rgba(251,146,60,0.06) 0%, transparent 70%); top: 50%; right: -100px; animation: orbFloat3 22s ease-in-out infinite; }
@keyframes orbFloat1 { 0%, 100% { transform: translate(0, 0) scale(1); } 33% { transform: translate(-80px, 60px) scale(1.1); } 66% { transform: translate(40px, -40px) scale(0.9); } }
@keyframes orbFloat2 { 0%, 100% { transform: translate(0, 0) scale(1); } 33% { transform: translate(60px, -80px) scale(1.15); } 66% { transform: translate(-40px, 40px) scale(0.95); } }
@keyframes orbFloat3 { 0%, 100% { transform: translate(0, 0) scale(1); } 50% { transform: translate(-60px, -60px) scale(1.1); } }

/* ===== Navbar ===== */
.navbar { position: fixed; top: 0; left: 0; right: 0; z-index: 1000; padding: var(--space-md) 0; transition: all var(--duration-normal) var(--ease-out); background: transparent; }
.navbar.scrolled { background: rgba(9, 9, 11, 0.85); backdrop-filter: blur(20px) saturate(1.5); -webkit-backdrop-filter: blur(20px) saturate(1.5); border-bottom: 1px solid var(--border-subtle); padding: var(--space-sm) 0; }
.nav-container { max-width: 1200px; margin: 0 auto; padding: 0 var(--space-xl); display: flex; align-items: center; justify-content: space-between; }
.nav-logo { display: flex; align-items: center; gap: var(--space-sm); text-decoration: none; color: var(--text-primary); font-weight: 600; font-size: 1.1rem; letter-spacing: -0.02em; }
.logo-icon { display: flex; align-items: center; }
.logo-highlight { background: var(--accent-gradient); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; font-weight: 700; }
.nav-links { display: flex; align-items: center; gap: var(--space-xs); }
.nav-link { text-decoration: none; color: var(--text-secondary); font-size: 0.875rem; font-weight: 450; padding: var(--space-sm) var(--space-md); border-radius: var(--radius-sm); transition: all var(--duration-fast) var(--ease-out); }
.nav-link:hover { color: var(--text-primary); background: var(--bg-glass-hover); }
.nav-toggle { display: none; flex-direction: column; gap: 5px; background: none; border: none; cursor: pointer; padding: var(--space-sm); }
.nav-toggle span { display: block; width: 22px; height: 2px; background: var(--text-secondary); border-radius: 2px; transition: all var(--duration-normal) var(--ease-out); }

/* ===== Hero ===== */
.hero {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    position: relative;
    z-index: 1;
    padding: 120px var(--space-xl) var(--space-3xl);
    max-width: 1200px;
    margin: 0 auto;
    gap: var(--space-2xl);
}
.hero-content {
    max-width: 800px;
    margin: 0 auto;
}
.hero-title {
    font-family: var(--font-display);
    font-size: clamp(2.2rem, 5vw, 3.8rem);
    font-weight: 700;
    line-height: 1.2;
    letter-spacing: -0.03em;
    margin-bottom: var(--space-lg);
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: fadeInUp 0.8s var(--ease-out) 0.1s both;
}
.hero-intro {
    font-size: 1.1rem;
    color: var(--text-secondary);
    line-height: 1.75;
    margin-bottom: var(--space-md);
    animation: fadeInUp 0.8s var(--ease-out) 0.25s both;
}
.hero-intro strong {
    color: var(--text-primary);
}
.hero-intro-secondary {
    font-size: 0.95rem;
    color: var(--text-tertiary);
    line-height: 1.7;
    margin-bottom: var(--space-xl);
    animation: fadeInUp 0.8s var(--ease-out) 0.4s both;
}
.hero-intro-secondary strong {
    color: var(--text-secondary);
}
.hero-cta {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 14px 28px;
    background: var(--accent-gradient);
    color: #fff;
    text-decoration: none;
    font-weight: 600;
    font-size: 0.95rem;
    border-radius: var(--radius-lg);
    transition: all var(--duration-normal) var(--ease-out);
    box-shadow: 0 4px 24px rgba(167,139,250,0.3);
    animation: fadeInUp 0.8s var(--ease-out) 0.55s both;
    margin-bottom: var(--space-xl);
}
.hero-cta:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 32px rgba(167,139,250,0.4);
}
.hero-cta svg {
    transition: transform var(--duration-fast) var(--ease-out);
}
.hero-cta:hover svg {
    transform: translateX(4px);
}
.hero-visual {
    width: 100%;
    max-width: 850px;
    animation: fadeInUp 0.8s var(--ease-out) 0.6s both;
}

/* ===== Shared Section Styles ===== */
.section-container { max-width: 1200px; margin: 0 auto; padding: 0 var(--space-xl); }
.section-header { text-align: center; margin-bottom: var(--space-2xl); }
.section-tag { display: inline-block; font-size: 0.75rem; font-weight: 600; letter-spacing: 0.1em; text-transform: uppercase; color: var(--accent-violet); background: rgba(167,139,250,0.1); border: 1px solid rgba(167,139,250,0.15); padding: var(--space-xs) var(--space-md); border-radius: var(--radius-full); margin-bottom: var(--space-md); }
.section-title { font-family: var(--font-display); font-size: clamp(1.6rem, 3.5vw, 2.4rem); font-weight: 700; letter-spacing: -0.03em; margin-bottom: var(--space-sm); background: linear-gradient(135deg, var(--text-primary) 0%, var(--text-secondary) 100%); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.section-desc { font-size: 1rem; color: var(--text-tertiary); max-width: 560px; margin: 0 auto; line-height: 1.7; }
.section-intro { font-size: 1rem; color: var(--text-secondary); line-height: 1.7; margin-bottom: var(--space-xl); max-width: 800px; }
.section-intro strong, .section-intro b { color: var(--text-primary); }
.section-note { font-size: 0.9rem; color: var(--text-tertiary); line-height: 1.7; margin-top: var(--space-xl); max-width: 800px; }
.section-note b, .section-note strong { color: var(--text-secondary); }
.content-section { position: relative; z-index: 1; padding: var(--space-3xl) 0; border-top: 1px solid var(--border-subtle); }

/* ===== Converter ===== */
.converter-section { position: relative; z-index: 1; padding: 0 0 var(--space-3xl); }
.converter-card { background: var(--bg-card); backdrop-filter: blur(24px) saturate(1.3); border: 1px solid var(--border-subtle); border-radius: var(--radius-2xl); padding: var(--space-2xl); box-shadow: var(--shadow-xl), var(--shadow-glow); position: relative; overflow: hidden; }
.converter-card::before { content: ''; position: absolute; top: 0; left: 0; right: 0; height: 1px; background: linear-gradient(90deg, transparent, rgba(167,139,250,0.4), rgba(244,114,182,0.3), transparent); }
.converter-grid { display: grid; grid-template-columns: 1fr auto 1fr; gap: var(--space-xl); align-items: start; }
.input-group { display: flex; flex-direction: column; gap: var(--space-md); }
.input-label { display: flex; align-items: center; gap: var(--space-sm); font-size: 0.85rem; font-weight: 500; color: var(--text-secondary); }
.label-icon { display: flex; color: var(--accent-violet); opacity: 0.7; }
.input-wrapper { position: relative; }
.converter-input { width: 100%; padding: 18px 60px 18px 20px; background: var(--bg-glass); border: 1px solid var(--border-medium); border-radius: var(--radius-lg); color: var(--text-primary); font-size: 1.8rem; font-weight: 600; font-family: var(--font-sans); letter-spacing: -0.02em; transition: all var(--duration-normal) var(--ease-out); outline: none; -moz-appearance: textfield; }
.converter-input::-webkit-outer-spin-button, .converter-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.converter-input::placeholder { color: var(--text-muted); font-weight: 400; }
.converter-input:focus { border-color: var(--accent-violet); box-shadow: 0 0 0 3px rgba(167,139,250,0.15), var(--shadow-glow); background: rgba(167,139,250,0.04); }
.input-unit { position: absolute; right: 20px; top: 50%; transform: translateY(-50%); font-size: 0.85rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; }
.input-presets { display: flex; flex-wrap: wrap; gap: var(--space-xs); }
.preset-btn { padding: 6px 12px; background: var(--bg-glass); border: 1px solid var(--border-subtle); border-radius: var(--radius-sm); color: var(--text-tertiary); font-size: 0.75rem; font-weight: 500; cursor: pointer; transition: all var(--duration-fast) var(--ease-out); font-family: var(--font-sans); }
.preset-btn:hover { background: rgba(167,139,250,0.1); border-color: var(--accent-violet); color: var(--accent-violet); transform: translateY(-1px); }
.swap-area { display: flex; flex-direction: column; align-items: center; gap: var(--space-sm); padding-top: 36px; }
.swap-btn { width: 48px; height: 48px; border-radius: 50%; background: var(--bg-glass); border: 1px solid var(--border-medium); color: var(--text-secondary); cursor: pointer; display: flex; align-items: center; justify-content: center; transition: all var(--duration-normal) var(--ease-spring); }
.swap-btn:hover { background: rgba(167,139,250,0.15); border-color: var(--accent-violet); color: var(--accent-violet); transform: rotate(180deg); box-shadow: var(--shadow-glow); }
.swap-label { font-size: 0.7rem; color: var(--text-muted); font-family: 'Courier New', monospace; font-weight: 600; }
.result-display { margin-top: var(--space-xl); padding: var(--space-lg) var(--space-xl); background: var(--accent-gradient-subtle); border: 1px solid rgba(167,139,250,0.1); border-radius: var(--radius-lg); text-align: center; transition: all var(--duration-normal) var(--ease-out); }
.result-display.active { border-color: rgba(167,139,250,0.25); box-shadow: 0 0 24px rgba(167,139,250,0.08); }
.result-text { font-size: 1.1rem; color: var(--text-secondary); font-weight: 500; transition: all var(--duration-normal) var(--ease-out); }
.result-display.active .result-text { color: var(--text-primary); font-size: 1.25rem; }
.formula-bar { display: flex; align-items: center; gap: var(--space-sm); margin-top: var(--space-lg); padding: var(--space-md) var(--space-lg); background: var(--bg-glass); border-radius: var(--radius-md); border: 1px solid var(--border-subtle); flex-wrap: wrap; }
.formula-label { font-size: 0.75rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; white-space: nowrap; }
.formula-code { font-family: 'Courier New', monospace; font-size: 0.8rem; color: var(--text-tertiary); background: none; }

/* ===== Definition Cards ===== */
.definition-grid { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-xl); margin-bottom: var(--space-2xl); }
.def-card { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); padding: var(--space-2xl); transition: all var(--duration-normal) var(--ease-out); }
.def-card:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); }
.def-card-header { display: flex; align-items: center; gap: var(--space-lg); margin-bottom: var(--space-lg); }
.def-icon { width: 64px; height: 80px; color: var(--accent-violet); }
.def-icon.oz-icon { color: var(--accent-pink); }
.def-unit { font-size: 2rem; font-weight: 800; letter-spacing: -0.03em; }
.def-card:first-child .def-unit { color: var(--accent-violet); }
.def-card:last-child .def-unit { color: var(--accent-pink); }
.def-name { font-size: 1.15rem; font-weight: 600; margin-bottom: var(--space-md); color: var(--text-primary); }
.def-text { font-size: 0.9rem; color: var(--text-tertiary); line-height: 1.7; margin-bottom: var(--space-md); }
.def-text b, .def-text strong { color: var(--text-secondary); font-weight: 600; }
.def-facts { display: grid; grid-template-columns: 1fr 1fr; gap: var(--space-sm); padding-top: var(--space-md); border-top: 1px solid var(--border-subtle); }
.fact-item { display: flex; flex-direction: column; gap: 2px; padding: var(--space-sm); }
.fact-label { font-size: 0.7rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; }
.fact-value { font-size: 0.8rem; color: var(--text-secondary); font-weight: 500; }

/* ===== Volume Comparison Diagram ===== */
.volume-comparison { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); padding: var(--space-2xl); }
.comparison-title { font-size: 1.1rem; font-weight: 600; margin-bottom: var(--space-xs); color: var(--text-primary); }
.comparison-desc { font-size: 0.9rem; color: var(--text-tertiary); line-height: 1.7; margin-bottom: var(--space-xl); }
.comparison-desc b { color: var(--text-secondary); }
.comparison-visual { display: flex; flex-direction: column; gap: var(--space-xl); }
.comparison-bar-group { display: flex; flex-direction: column; gap: var(--space-lg); }
.comparison-bar-container { display: flex; flex-direction: column; gap: var(--space-sm); }
.bar-label { font-size: 0.8rem; font-weight: 500; color: var(--text-secondary); }
.bar-track { height: 40px; background: var(--bg-glass); border: 1px solid var(--border-subtle); border-radius: var(--radius-md); overflow: hidden; position: relative; }
.bar-fill { height: 100%; border-radius: var(--radius-md); display: flex; align-items: center; justify-content: flex-end; padding: 0 12px; transition: width 0.5s var(--ease-out); min-width: 80px; }
.bar-fill.ml-bar { background: linear-gradient(90deg, rgba(167,139,250,0.3), rgba(167,139,250,0.5)); }
.bar-fill.oz-bar { background: linear-gradient(90deg, rgba(244,114,182,0.3), rgba(244,114,182,0.5)); }
.bar-value { font-size: 0.75rem; font-weight: 600; color: var(--text-primary); white-space: nowrap; }
.comparison-slider-area { margin-top: var(--space-md); }

/* ===== Difference Table ===== */
.diff-table-wrapper { overflow-x: auto; margin-bottom: var(--space-md); }
.diff-table { width: 100%; border-collapse: collapse; background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-lg); overflow: hidden; }
.diff-table th { padding: 14px 20px; text-align: left; font-size: 0.75rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; background: rgba(0,0,0,0.3); border-bottom: 1px solid var(--border-subtle); }
.diff-table td { padding: 14px 20px; font-size: 0.88rem; color: var(--text-secondary); border-bottom: 1px solid var(--border-subtle); line-height: 1.6; }
.diff-table td strong { color: var(--text-primary); }
.diff-table tbody tr:hover { background: rgba(167,139,250,0.03); }
.diff-table tbody tr:last-child td { border-bottom: none; }

/* ===== Formula Section ===== */
.formula-diagram { display: flex; gap: var(--space-lg); margin-bottom: var(--space-2xl); flex-wrap: wrap; }
.formula-box { flex: 1; min-width: 260px; padding: var(--space-xl); background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); text-align: center; transition: all var(--duration-normal) var(--ease-out); }
.formula-box:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); }
.formula-box.main-formula { border-color: rgba(167,139,250,0.2); }
.formula-display { display: block; font-family: 'Courier New', monospace; font-size: 1.3rem; font-weight: 700; color: var(--text-primary); margin-bottom: var(--space-sm); letter-spacing: 0.01em; }
.formula-sub { font-size: 0.8rem; color: var(--text-muted); }

/* Formula Flow Interactive */
.formula-flow-interactive { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); padding: var(--space-2xl); }
.flow-title { font-size: 1rem; font-weight: 600; color: var(--accent-violet); margin-bottom: var(--space-xl); }
.flow-pipeline { display: flex; align-items: center; gap: var(--space-md); flex-wrap: wrap; justify-content: center; margin-bottom: var(--space-lg); }
.pipeline-step { display: flex; flex-direction: column; align-items: center; gap: var(--space-sm); }
.pipeline-label { font-size: 0.7rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; }
.pipeline-input { width: 120px; padding: 12px 16px; background: var(--bg-glass); border: 1px solid var(--border-medium); border-radius: var(--radius-md); color: var(--text-primary); font-size: 1.4rem; font-weight: 700; font-family: var(--font-sans); text-align: center; outline: none; -moz-appearance: textfield; transition: all var(--duration-normal) var(--ease-out); }
.pipeline-input::-webkit-outer-spin-button, .pipeline-input::-webkit-inner-spin-button { -webkit-appearance: none; }
.pipeline-input:focus { border-color: var(--accent-violet); box-shadow: 0 0 0 3px rgba(167,139,250,0.15); }
.pipeline-value { font-family: 'Courier New', monospace; font-size: 1.1rem; font-weight: 700; color: var(--accent-pink); padding: 12px 16px; background: rgba(244,114,182,0.08); border: 1px solid rgba(244,114,182,0.15); border-radius: var(--radius-md); }
.pipeline-result { font-size: 1.4rem; font-weight: 700; color: var(--accent-orange); padding: 12px 16px; background: rgba(251,146,60,0.08); border: 1px solid rgba(251,146,60,0.15); border-radius: var(--radius-md); transition: all var(--duration-normal) var(--ease-out); min-width: 100px; text-align: center; }
.pipeline-arrow { display: flex; align-items: center; padding-top: 20px; }
.flow-sentence { font-size: 0.95rem; color: var(--text-secondary); text-align: center; padding: var(--space-md) var(--space-lg); background: var(--accent-gradient-subtle); border-radius: var(--radius-md); border: 1px solid rgba(167,139,250,0.08); }
.flow-sentence strong { color: var(--text-primary); }

/* ===== Examples Grid ===== */
.examples-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: var(--space-md); }
.example-card { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-lg); overflow: hidden; cursor: pointer; transition: all var(--duration-normal) var(--ease-out); }
.example-card:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); transform: translateY(-2px); }
.example-card.expanded { border-color: rgba(167,139,250,0.3); }
.ex-header { display: flex; align-items: center; gap: var(--space-md); padding: var(--space-lg); }
.ex-input { font-size: 1.1rem; font-weight: 700; color: var(--accent-violet); }
.ex-equals { color: var(--text-muted); font-size: 0.9rem; }
.ex-result { font-size: 1.1rem; font-weight: 700; color: var(--accent-pink); }
.ex-details { max-height: 0; overflow: hidden; transition: max-height var(--duration-slow) var(--ease-out), padding var(--duration-slow) var(--ease-out); }
.example-card.expanded .ex-details { max-height: 200px; padding: 0 var(--space-lg) var(--space-lg); }
.ex-calc { font-family: 'Courier New', monospace; font-size: 0.85rem; color: var(--text-tertiary); margin-bottom: var(--space-sm); padding: var(--space-sm) var(--space-md); background: var(--bg-glass); border-radius: var(--radius-sm); }
.ex-calc strong { color: var(--accent-orange); }
.ex-context { font-size: 0.8rem; color: var(--text-muted); line-height: 1.6; font-style: italic; }

/* ===== Tables ===== */
.table-section .section-header { text-align: left; }
.table-card { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); overflow: hidden; box-shadow: var(--shadow-lg); }
.table-wrapper { overflow-x: auto; }
.conversion-table { width: 100%; border-collapse: collapse; }
.conversion-table th { padding: 14px 20px; text-align: left; font-size: 0.75rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; border-bottom: 1px solid var(--border-subtle); background: rgba(0,0,0,0.2); }
.conversion-table td { padding: 14px 20px; font-size: 0.9rem; color: var(--text-secondary); border-bottom: 1px solid var(--border-subtle); transition: all var(--duration-fast) var(--ease-out); }
.conversion-table tbody tr { cursor: pointer; transition: all var(--duration-fast) var(--ease-out); }
.conversion-table tbody tr:hover { background: rgba(167,139,250,0.05); }
.conversion-table tbody tr:hover td { color: var(--text-primary); }
.conversion-table tbody tr:last-child td { border-bottom: none; }
.conversion-table td:first-child { font-weight: 600; color: var(--accent-violet); }
.conversion-table td:nth-child(2) { font-weight: 600; color: var(--accent-pink); }
.conversion-table td:nth-child(3) { color: var(--accent-orange); font-weight: 500; }
.conversion-table td:last-child { font-size: 0.8rem; color: var(--text-muted); font-style: italic; }

/* ===== US vs Imperial ===== */
.imperial-comparison { display: flex; flex-direction: column; gap: var(--space-2xl); }
.imp-cards { display: grid; grid-template-columns: 1fr auto 1fr; gap: var(--space-xl); align-items: center; }
.imp-card { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); padding: var(--space-2xl); transition: all var(--duration-normal) var(--ease-out); }
.imp-card:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); }
.imp-flag { font-size: 2rem; margin-bottom: var(--space-md); }
.imp-card h3 { font-size: 1rem; font-weight: 600; color: var(--text-primary); margin-bottom: var(--space-md); }
.imp-value { font-size: 1.8rem; font-weight: 800; margin-bottom: var(--space-lg); letter-spacing: -0.02em; }
.us-card .imp-value { color: var(--accent-violet); }
.uk-card .imp-value { color: var(--accent-pink); }
.imp-details { list-style: none; display: flex; flex-direction: column; gap: var(--space-sm); }
.imp-details li { font-size: 0.85rem; color: var(--text-tertiary); line-height: 1.6; padding-left: var(--space-md); position: relative; }
.imp-details li::before { content: ''; position: absolute; left: 0; top: 8px; width: 5px; height: 5px; border-radius: 50%; }
.us-card .imp-details li::before { background: var(--accent-violet); }
.uk-card .imp-details li::before { background: var(--accent-pink); }
.imp-vs { text-align: center; }
.imp-vs-text { display: block; font-size: 1.5rem; font-weight: 800; color: var(--text-muted); margin-bottom: var(--space-sm); }
.imp-vs-diff { font-size: 0.75rem; color: var(--accent-orange); font-weight: 600; background: rgba(251,146,60,0.1); padding: 4px 12px; border-radius: var(--radius-full); border: 1px solid rgba(251,146,60,0.15); }
.imp-bar-comparison { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); padding: var(--space-2xl); }
.imp-bar-title { font-size: 1rem; font-weight: 600; color: var(--text-primary); margin-bottom: var(--space-xl); }
.imp-bars { display: flex; flex-direction: column; gap: var(--space-lg); margin-bottom: var(--space-lg); }
.imp-bar-row { display: flex; align-items: center; gap: var(--space-lg); }
.imp-bar-label { font-size: 0.8rem; font-weight: 600; color: var(--text-secondary); min-width: 70px; }
.imp-bar-track { flex: 1; height: 44px; background: var(--bg-glass); border: 1px solid var(--border-subtle); border-radius: var(--radius-md); overflow: hidden; }
.imp-bar-fill { height: 100%; display: flex; align-items: center; padding: 0 16px; font-size: 0.85rem; font-weight: 600; color: var(--text-primary); border-radius: var(--radius-md); transition: width 1s var(--ease-out); }
.imp-bar-fill.us-fill { width: 100%; background: linear-gradient(90deg, rgba(167,139,250,0.25), rgba(167,139,250,0.45)); }
.imp-bar-fill.uk-fill { width: 96.08%; background: linear-gradient(90deg, rgba(244,114,182,0.25), rgba(244,114,182,0.45)); }
.imp-bar-note { font-size: 0.85rem; color: var(--text-tertiary); line-height: 1.7; }

/* ===== Abbreviations ===== */
.abbrev-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: var(--space-md); }
.abbrev-card { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-lg); padding: var(--space-lg); text-align: center; transition: all var(--duration-normal) var(--ease-out); }
.abbrev-card:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); transform: translateY(-2px); }
.abbrev-symbol { font-size: 2rem; font-weight: 800; color: var(--accent-violet); margin-bottom: var(--space-sm); letter-spacing: -0.02em; font-family: 'Courier New', monospace; }
.abbrev-card:nth-child(3) .abbrev-symbol,
.abbrev-card:nth-child(4) .abbrev-symbol { color: var(--accent-pink); }
.abbrev-card:nth-child(5) .abbrev-symbol,
.abbrev-card:nth-child(6) .abbrev-symbol { color: var(--accent-orange); }
.abbrev-name { font-size: 0.9rem; font-weight: 600; color: var(--text-primary); margin-bottom: var(--space-xs); }
.abbrev-note { font-size: 0.75rem; color: var(--text-muted); line-height: 1.5; }

/* ===== Usage Section ===== */
.usage-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-xl); }
.usage-card { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-xl); padding: var(--space-2xl); transition: all var(--duration-normal) var(--ease-out); }
.usage-card:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); transform: translateY(-2px); }
.usage-icon { color: var(--accent-violet); margin-bottom: var(--space-lg); }
.usage-card:nth-child(2) .usage-icon { color: var(--accent-pink); }
.usage-card:nth-child(3) .usage-icon { color: var(--accent-orange); }
.usage-card h3 { font-size: 1rem; font-weight: 600; color: var(--text-primary); margin-bottom: var(--space-md); }
.usage-card p { font-size: 0.88rem; color: var(--text-tertiary); line-height: 1.7; }
.usage-card p b, .usage-card p strong { color: var(--text-secondary); font-weight: 600; }

/* ===== Subpage Links Section ===== */
.subpages-section { padding-top: var(--space-2xl); }
.subpage-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: var(--space-md); }
.subpage-card { display: flex; flex-direction: column; gap: var(--space-xs); min-height: 150px; padding: var(--space-xl); background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-lg); text-decoration: none; transition: all var(--duration-normal) var(--ease-out); }
.subpage-card:hover { border-color: var(--border-accent); box-shadow: var(--shadow-glow); transform: translateY(-2px); }
.subpage-label { width: fit-content; font-size: 0.68rem; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; color: var(--accent-violet); background: rgba(167,139,250,0.1); border: 1px solid rgba(167,139,250,0.14); border-radius: var(--radius-full); padding: 4px 10px; }
.subpage-card:nth-child(2n) .subpage-label { color: var(--accent-pink); background: rgba(244,114,182,0.1); border-color: rgba(244,114,182,0.14); }
.subpage-card:nth-child(3n) .subpage-label { color: var(--accent-orange); background: rgba(251,146,60,0.1); border-color: rgba(251,146,60,0.14); }
.subpage-title { color: var(--text-primary); font-size: 1rem; font-weight: 650; line-height: 1.35; margin-top: var(--space-xs); }
.subpage-desc { color: var(--text-tertiary); font-size: 0.84rem; line-height: 1.6; }

/* ===== FAQ Section ===== */
.faq-section { padding-bottom: var(--space-4xl); }
.faq-grid { display: flex; flex-direction: column; gap: var(--space-sm); max-width: 800px; margin: 0 auto; }
.faq-item { background: var(--bg-card); border: 1px solid var(--border-subtle); border-radius: var(--radius-lg); overflow: hidden; transition: all var(--duration-normal) var(--ease-out); }
.faq-item:hover { border-color: var(--border-medium); }
.faq-item.active { border-color: var(--border-accent); box-shadow: var(--shadow-glow); }
.faq-question { width: 100%; display: flex; align-items: center; justify-content: space-between; padding: var(--space-lg) var(--space-xl); background: none; border: none; color: var(--text-primary); font-size: 0.95rem; font-weight: 500; text-align: left; cursor: pointer; font-family: var(--font-sans); line-height: 1.5; transition: color var(--duration-fast) var(--ease-out); }
.faq-question:hover { color: var(--accent-violet); }
.faq-icon { flex-shrink: 0; display: flex; align-items: center; justify-content: center; width: 32px; height: 32px; border-radius: 50%; background: var(--bg-glass); color: var(--text-muted); transition: all var(--duration-normal) var(--ease-out); margin-left: var(--space-md); }
.faq-item.active .faq-icon { background: rgba(167,139,250,0.15); color: var(--accent-violet); transform: rotate(180deg); }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height var(--duration-slow) var(--ease-out), padding var(--duration-slow) var(--ease-out); }
.faq-item.active .faq-answer { max-height: 400px; padding: 0 var(--space-xl) var(--space-xl); }
.faq-answer p { font-size: 0.9rem; color: var(--text-tertiary); line-height: 1.7; }
.faq-answer p b, .faq-answer p strong { color: var(--text-secondary); font-weight: 600; }

/* ===== Footer ===== */
.footer { position: relative; z-index: 1; padding: var(--space-4xl) 0 var(--space-xl); border-top: 1px solid var(--border-subtle); background: var(--bg-secondary); }
.footer-grid { display: grid; grid-template-columns: minmax(260px, 1.5fr) repeat(4, minmax(130px, 1fr)); gap: var(--space-3xl); margin-bottom: var(--space-3xl); }
.footer-logo { display: flex; align-items: center; gap: var(--space-sm); text-decoration: none; color: var(--text-primary); font-weight: 600; font-size: 1rem; margin-bottom: var(--space-md); }
.footer-desc { font-size: 0.83rem; color: var(--text-muted); line-height: 1.7; max-width: 360px; }
.footer-heading { font-size: 0.75rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: var(--space-lg); }
.footer-links-group { display: flex; flex-direction: column; gap: var(--space-sm); }
.footer-link { text-decoration: none; color: var(--text-tertiary); font-size: 0.83rem; transition: color var(--duration-fast) var(--ease-out); }
.footer-link:hover { color: var(--accent-violet); }
.footer-bottom { display: flex; align-items: center; justify-content: space-between; padding-top: var(--space-xl); border-top: 1px solid var(--border-subtle); font-size: 0.8rem; color: var(--text-muted); flex-wrap: wrap; gap: var(--space-sm); }
.footer-note { font-family: 'Courier New', monospace; font-size: 0.72rem; color: var(--text-muted); opacity: 0.9; }

.footer-contact {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
    margin-top: var(--space-lg);
}
.contact-item {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    transition: color var(--duration-fast) var(--ease-out);
}
.contact-item:hover {
    color: var(--accent-violet);
}
.contact-icon {
    color: var(--accent-violet);
    opacity: 0.8;
}
.footer-social {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
    margin-top: var(--space-lg);
}
.footer-social-label {
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-muted);
}
.footer-social-links {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
}
.footer-social-link {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 10px;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    background: var(--bg-glass);
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.78rem;
    transition: all var(--duration-fast) var(--ease-out);
}
.footer-social-link:hover {
    color: var(--accent-violet);
    border-color: var(--border-accent);
    background: rgba(167,139,250,0.08);
}
.footer-language-links {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 6px 10px;
}
.footer-language-link {
    color: var(--text-tertiary);
    text-decoration: none;
    font-size: 0.78rem;
    transition: color var(--duration-fast) var(--ease-out);
}
.footer-language-link:hover,
.footer-language-link.active {
    color: var(--accent-violet);
}

/* ===== Readability Adjustments ===== */
.hero-intro-secondary,
.section-desc,
.section-intro {
    font-size: 1.06rem;
    line-height: 1.85;
}

.section-note,
.def-text,
.comparison-desc,
.usage-card p,
.faq-answer p,
.imp-details li,
.imp-bar-note,
.subpage-desc {
    font-size: 0.96rem;
    line-height: 1.85;
}

.diff-table td,
.conversion-table td {
    font-size: 0.95rem;
    line-height: 1.72;
}

.conversion-table td:last-child,
.ex-context,
.abbrev-note,
.footer-desc,
.footer-link,
.footer-language-link,
.contact-item {
    font-size: 0.9rem;
    line-height: 1.7;
}

.section-tag,
.formula-label,
.fact-label,
.pipeline-label,
.diff-table th,
.conversion-table th,
.footer-heading,
.footer-social-label,
.subpage-label {
    font-size: 0.78rem;
}

.preset-btn,
.formula-code,
.formula-sub,
.bar-label,
.imp-bar-label,
.footer-bottom {
    font-size: 0.86rem;
}

/* ===== Back to Top ===== */
.back-to-top {
    position: fixed;
    right: 24px;
    bottom: 24px;
    z-index: 1100;
    width: 46px;
    height: 46px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-medium);
    border-radius: 50%;
    background: rgba(17, 24, 39, 0.92);
    color: var(--text-primary);
    box-shadow: var(--shadow-lg);
    cursor: pointer;
    opacity: 0;
    pointer-events: none;
    transform: translateY(12px);
    transition: opacity var(--duration-normal) var(--ease-out), transform var(--duration-normal) var(--ease-out), border-color var(--duration-fast) var(--ease-out), color var(--duration-fast) var(--ease-out);
}
.back-to-top.visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}
.back-to-top:hover {
    border-color: var(--accent-violet);
    color: var(--accent-violet);
}

/* ===== Slider (shared) ===== */
.diagram-slider { width: 100%; height: 6px; -webkit-appearance: none; appearance: none; background: var(--bg-glass); border-radius: 3px; outline: none; border: 1px solid var(--border-subtle); cursor: pointer; }
.diagram-slider::-webkit-slider-thumb { -webkit-appearance: none; width: 22px; height: 22px; border-radius: 50%; background: var(--accent-gradient); cursor: pointer; box-shadow: 0 0 12px rgba(167,139,250,0.4); transition: transform var(--duration-fast) var(--ease-spring); }
.diagram-slider::-webkit-slider-thumb:hover { transform: scale(1.15); }
.diagram-slider::-moz-range-thumb { width: 22px; height: 22px; border-radius: 50%; background: var(--accent-gradient); cursor: pointer; border: none; box-shadow: 0 0 12px rgba(167,139,250,0.4); }
.slider-labels { display: flex; justify-content: space-between; margin-top: var(--space-sm); font-size: 0.7rem; color: var(--text-muted); }
.slider-current { color: var(--accent-violet); font-weight: 600; }

/* ===== Animations ===== */
@keyframes fadeInUp { from { opacity: 0; transform: translateY(24px); } to { opacity: 1; transform: translateY(0); } }

/* Scroll reveal */
.def-card, .volume-comparison, .formula-box, .formula-flow-interactive, .example-card,
.table-card, .imp-card, .imp-bar-comparison, .abbrev-card, .usage-card, .faq-item,
.converter-card, .diff-table-wrapper { opacity: 0; transform: translateY(20px); transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out); }
.def-card.visible, .volume-comparison.visible, .formula-box.visible,
.formula-flow-interactive.visible, .example-card.visible, .table-card.visible,
.imp-card.visible, .imp-bar-comparison.visible, .abbrev-card.visible,
.usage-card.visible, .faq-item.visible, .converter-card.visible, .diff-table-wrapper.visible { opacity: 1; transform: translateY(0); }

/* ===== Responsive ===== */
@media (max-width: 1024px) {
    .imp-cards { grid-template-columns: 1fr; gap: var(--space-md); }
    .imp-vs { display: flex; align-items: center; gap: var(--space-md); justify-content: center; }
    .usage-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
    .footer-brand { grid-column: 1 / -1; }
}
@media (max-width: 768px) {
    .hero { flex-direction: column; text-align: center; padding-top: 100px; min-height: auto; gap: var(--space-2xl); }
    .hero-content { max-width: 100%; }
    .hero-visual { order: -1; }
    .hero-beaker { width: 140px; height: 200px; }
    .nav-links { display: none; position: absolute; top: 100%; left: 0; right: 0; flex-direction: column; background: rgba(9, 9, 11, 0.95); backdrop-filter: blur(20px); border-bottom: 1px solid var(--border-subtle); padding: var(--space-md); }
    .nav-links.open { display: flex; }
    .nav-toggle { display: flex; }
    .converter-grid { grid-template-columns: 1fr; gap: var(--space-md); }
    .swap-area { flex-direction: row; padding-top: 0; }
    .converter-input { font-size: 1.4rem; }
    .definition-grid { grid-template-columns: 1fr; }
    .formula-diagram { flex-direction: column; }
    .flow-pipeline { flex-direction: column; }
    .pipeline-arrow { transform: rotate(90deg); }
    .examples-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: var(--space-xl); }
    .footer-brand { grid-column: auto; }
    .footer-bottom { flex-direction: column; text-align: center; }
    .table-card { margin: 0 calc(-1 * var(--space-md)); border-radius: var(--radius-lg); }
    .abbrev-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 480px) {
    .section-container { padding: 0 var(--space-md); }
    .back-to-top { right: 16px; bottom: 16px; width: 42px; height: 42px; }
    .converter-card { padding: var(--space-lg); }
    .hero-title { font-size: 2rem; }
    .section-title { font-size: 1.4rem; }
    .converter-input { font-size: 1.2rem; padding: 14px 50px 14px 14px; }
    .preset-btn { padding: 5px 10px; font-size: 0.7rem; }
    .abbrev-grid { grid-template-columns: 1fr 1fr; }
    .imp-card { padding: var(--space-lg); }
    .def-card { padding: var(--space-lg); }
    .def-card-header { flex-direction: column; align-items: flex-start; }
}