/* ===== CSS Variables & Reset ===== */
:root {
    --bg-primary: #eef2ff;
    --bg-secondary: #e0e7ff;
    --bg-card: rgba(255, 255, 255, 0.75);
    --bg-glass: rgba(255, 255, 255, 0.5);
    --text-primary: #1e1b4b;
    --text-secondary: #4338ca;
    --text-muted: #6366f1;
    --accent-1: #6366f1;
    --accent-2: #8b5cf6;
    --accent-3: #7c3aed;
    --accent-4: #a855f7;
    --green: #059669;
    --red: #dc2626;
    --orange: #ea580c;
    --blue: #2563eb;
    --cyan: #0891b2;
    --border: rgba(99, 102, 241, 0.25);
    --shadow: 0 8px 32px rgba(99, 102, 241, 0.12);
    --radius: 16px;
    --radius-sm: 10px;
    --font: 'Inter', -apple-system, sans-serif;
    --mono: 'JetBrains Mono', monospace;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: var(--font);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: hidden;
}

/* ===== Canvas ===== */
#particleCanvas {
    position: fixed; top: 0; left: 0;
    width: 100%; height: 100%;
    z-index: 0; pointer-events: none;
}

/* ===== Layout ===== */
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.section { position: relative; z-index: 1; padding: 100px 0; }
.section-dark { background: var(--bg-secondary); }

.section-header { text-align: center; margin-bottom: 60px; }
.section-badge {
    display: inline-block; padding: 6px 18px;
    background: rgba(99, 102, 241, 0.12); border: 1px solid var(--border);
    border-radius: 20px; font-size: 0.85rem; color: var(--accent-3);
    margin-bottom: 16px; letter-spacing: 0.5px;
}
.section-title { font-size: 2.5rem; font-weight: 800; margin-bottom: 12px; color: var(--text-primary); }
.section-desc { color: var(--text-secondary); font-size: 1.1rem; max-width: 600px; margin: 0 auto; }

/* ===== Hero ===== */
.hero {
    position: relative; z-index: 1;
    min-height: 100vh; display: flex; flex-direction: column;
    align-items: center; justify-content: center; text-align: center;
    padding: 40px 24px;
    background: linear-gradient(160deg, #eef2ff 0%, #ddd6fe 40%, #c7d2fe 70%, #e0f2fe 100%);
}
.hero-badge {
    display: inline-block; padding: 8px 20px;
    background: rgba(99, 102, 241, 0.12); border: 1px solid var(--border);
    border-radius: 24px; font-size: 0.9rem; color: var(--accent-3);
    margin-bottom: 28px; animation: fadeInUp 0.8s ease;
    backdrop-filter: blur(8px);
}
.hero-title {
    font-size: clamp(2.5rem, 6vw, 4.5rem); font-weight: 900;
    line-height: 1.1; margin-bottom: 20px;
    animation: fadeInUp 0.8s ease 0.15s both;
    color: var(--text-primary);
}
.gradient-text {
    background: linear-gradient(135deg, #6366f1, #a855f7, #0891b2);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    background-clip: text;
}
.hero-subtitle {
    font-size: 1.15rem; color: var(--text-secondary);
    max-width: 560px; margin-bottom: 36px;
    animation: fadeInUp 0.8s ease 0.3s both;
}
.hero-actions {
    display: flex; gap: 16px; flex-wrap: wrap; justify-content: center;
    animation: fadeInUp 0.8s ease 0.45s both;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 14px 28px; border-radius: var(--radius-sm);
    font-family: var(--font); font-size: 1rem; font-weight: 600;
    cursor: pointer; border: none; transition: all 0.3s ease;
}
.btn-icon { font-size: 1.1rem; }
.btn-primary {
    background: linear-gradient(135deg, var(--accent-1), var(--accent-2));
    color: white; box-shadow: 0 4px 20px rgba(99, 102, 241, 0.35);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 30px rgba(99, 102, 241, 0.5); }
.btn-secondary {
    background: var(--bg-glass); color: var(--text-primary);
    border: 1px solid var(--border); backdrop-filter: blur(8px);
}
.btn-secondary:hover { background: rgba(99, 102, 241, 0.12); border-color: var(--accent-1); }
.btn-full { width: 100%; justify-content: center; margin-top: 16px; }

/* ===== Formula Card ===== */
.formula-card {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 48px; max-width: 800px;
    margin: 0 auto; backdrop-filter: blur(12px);
    box-shadow: var(--shadow);
}
.formula-wrapper { margin-bottom: 40px; }
.formula-main { display: flex; justify-content: center; align-items: center; }
.formula-fraction { display: flex; align-items: center; gap: 16px; font-size: 1.5rem; }
.formula-part {
    padding: 8px 16px; border-radius: 8px; font-family: var(--mono);
    font-weight: 600; transition: all 0.3s ease; cursor: default;
}
.formula-equals, .formula-multiply { color: var(--text-muted); font-weight: 300; }
.fraction { display: flex; flex-direction: column; align-items: center; }
.fraction-top { display: flex; align-items: center; gap: 10px; padding-bottom: 8px; }
.fraction-line { width: 100%; height: 2px; background: var(--text-muted); }
.fraction-bottom { padding-top: 8px; }

.posterior { color: #0891b2; background: rgba(8, 145, 178, 0.12); }
.likelihood { color: #7c3aed; background: rgba(124, 58, 237, 0.1); }
.prior { color: #059669; background: rgba(5, 150, 105, 0.1); }
.evidence { color: #ea580c; background: rgba(234, 88, 12, 0.1); }

.formula-legend { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.legend-item {
    display: flex; align-items: flex-start; gap: 12px; padding: 12px;
    border-radius: var(--radius-sm); transition: background 0.3s;
    cursor: pointer;
}
.legend-item:hover { background: rgba(99, 102, 241, 0.08); }
.legend-color { width: 4px; height: 40px; border-radius: 2px; flex-shrink: 0; margin-top: 2px; }
.posterior-bg { background: var(--cyan); }
.likelihood-bg { background: var(--accent-3); }
.prior-bg { background: var(--green); }
.evidence-bg { background: var(--orange); }
.legend-text { display: flex; flex-direction: column; }
.legend-text strong { font-size: 0.9rem; margin-bottom: 2px; color: var(--text-primary); }
.legend-text span { font-size: 0.8rem; color: var(--text-secondary); }

/* ===== Architecture ===== */
.architecture-canvas {
    position: relative; padding: 40px 20px;
    background: rgba(255, 255, 255, 0.4); border-radius: var(--radius);
    border: 1px solid var(--border); min-height: 600px;
    overflow: hidden; backdrop-filter: blur(8px);
    box-shadow: var(--shadow);
}
.arch-connections { position: absolute; top: 0; left: 0; width: 100%; height: 100%; z-index: 0; pointer-events: none; }
.arch-layer {
    position: relative; z-index: 1; margin-bottom: 32px;
    display: flex; flex-direction: column; align-items: center;
}
.arch-layer:last-of-type { margin-bottom: 0; }
.layer-label {
    font-size: 0.75rem; text-transform: uppercase; letter-spacing: 2px;
    color: var(--text-muted); margin-bottom: 12px; font-weight: 600;
}
.arch-nodes { display: flex; gap: 20px; justify-content: center; flex-wrap: wrap; }

.arch-node {
    position: relative; padding: 20px 24px; min-width: 130px;
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius-sm); text-align: center;
    cursor: pointer; transition: all 0.4s ease;
    backdrop-filter: blur(8px); box-shadow: 0 4px 16px rgba(99, 102, 241, 0.08);
}
.arch-node:hover { transform: translateY(-4px); border-color: var(--accent-1); box-shadow: 0 8px 24px rgba(99, 102, 241, 0.18); }
.node-icon { font-size: 1.8rem; margin-bottom: 8px; }
.node-title { font-weight: 700; font-size: 0.9rem; color: var(--text-primary); }
.node-subtitle { font-size: 0.75rem; color: var(--text-secondary); font-family: var(--mono); margin-top: 4px; }

.node-pulse {
    position: absolute; top: 50%; left: 50%;
    width: 100%; height: 100%;
    transform: translate(-50%, -50%);
    border-radius: var(--radius-sm); opacity: 0;
    pointer-events: none;
}

.node-input { border-color: rgba(37, 99, 235, 0.3); }
.node-input:hover { box-shadow: 0 8px 30px rgba(37, 99, 235, 0.15); }
.node-feature { border-color: rgba(8, 145, 178, 0.3); }
.node-feature:hover { box-shadow: 0 8px 30px rgba(8, 145, 178, 0.15); }
.node-prob { border-color: rgba(124, 58, 237, 0.3); }
.node-prob:hover { box-shadow: 0 8px 30px rgba(124, 58, 237, 0.15); }
.node-bayes { border-color: rgba(99, 102, 241, 0.4); min-width: 260px; }
.node-bayes:hover { box-shadow: 0 8px 30px rgba(99, 102, 241, 0.2); }
.node-output { border-color: rgba(5, 150, 105, 0.3); }
.node-output:hover { box-shadow: 0 8px 30px rgba(5, 150, 105, 0.15); }

.arch-node.active-node {
    border-color: var(--accent-1) !important;
    box-shadow: 0 0 30px rgba(99, 102, 241, 0.3) !important;
}
.arch-node.active-node .node-pulse {
    animation: nodePulse 1s ease-out;
}

/* ===== Data Particles ===== */
.data-particle {
    position: absolute; width: 8px; height: 8px;
    border-radius: 50%; z-index: 2; pointer-events: none;
    box-shadow: 0 0 12px currentColor;
}

/* ===== Demo Section ===== */
.demo-container { display: grid; grid-template-columns: 1fr 1.2fr 1fr; gap: 24px; }
.demo-input-panel, .demo-process-panel, .demo-result-panel {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 28px;
    box-shadow: var(--shadow); backdrop-filter: blur(8px);
}
.panel-title { font-size: 1rem; font-weight: 700; margin-bottom: 20px; color: var(--text-primary); }

.email-option {
    display: block; width: 100%; text-align: left;
    padding: 14px 16px; margin-bottom: 10px;
    background: rgba(238, 242, 255, 0.6); border: 1px solid var(--border);
    border-radius: var(--radius-sm); color: var(--text-primary);
    cursor: pointer; transition: all 0.3s; font-family: var(--font); font-size: 0.85rem;
}
.email-option:hover { border-color: var(--accent-1); background: rgba(99, 102, 241, 0.1); }
.email-option.active { border-color: var(--accent-1); background: rgba(99, 102, 241, 0.14); box-shadow: 0 0 15px rgba(99, 102, 241, 0.12); }

.process-step {
    display: flex; align-items: flex-start; gap: 14px;
    padding: 14px; margin-bottom: 8px;
    border-radius: var(--radius-sm); transition: all 0.4s;
    opacity: 0.5;
}
.process-step.active { opacity: 1; background: rgba(99, 102, 241, 0.1); }
.process-step.done { opacity: 1; }
.step-number {
    width: 28px; height: 28px; border-radius: 50%; flex-shrink: 0;
    display: flex; align-items: center; justify-content: center;
    font-size: 0.75rem; font-weight: 700;
    background: rgba(99, 102, 241, 0.15); color: var(--accent-3);
    border: 1px solid var(--border);
}
.process-step.done .step-number { background: rgba(5, 150, 105, 0.15); color: var(--green); border-color: rgba(5, 150, 105, 0.3); }
.step-title { font-weight: 600; font-size: 0.85rem; color: var(--text-primary); }
.step-detail { font-size: 0.75rem; color: var(--text-secondary); margin-top: 4px; font-family: var(--mono); }
.step-status { margin-left: auto; font-size: 1rem; flex-shrink: 0; }

.result-placeholder { text-align: center; padding: 40px 20px; color: var(--text-muted); }
.result-placeholder-icon { font-size: 3rem; margin-bottom: 12px; }

.result-bars { margin-top: 20px; }
.result-bar-item { margin-bottom: 20px; }
.result-bar-label { display: flex; justify-content: space-between; margin-bottom: 8px; font-size: 0.9rem; font-weight: 600; color: var(--text-primary); }
.result-bar-track { height: 12px; background: rgba(99, 102, 241, 0.08); border-radius: 6px; overflow: hidden; }
.result-bar-fill {
    height: 100%; border-radius: 6px; transition: width 1s ease;
    background: linear-gradient(90deg, var(--accent-1), var(--accent-4));
}
.result-bar-fill.spam { background: linear-gradient(90deg, var(--red), var(--orange)); }
.result-bar-fill.ham { background: linear-gradient(90deg, var(--green), var(--cyan)); }

.result-verdict {
    text-align: center; margin-top: 24px; padding: 20px;
    border-radius: var(--radius-sm); font-size: 1.1rem; font-weight: 700;
}
.result-verdict.spam-verdict { background: rgba(220, 38, 38, 0.1); border: 1px solid rgba(220, 38, 38, 0.3); color: var(--red); }
.result-verdict.ham-verdict { background: rgba(5, 150, 105, 0.1); border: 1px solid rgba(5, 150, 105, 0.3); color: var(--green); }

/* ===== Info Cards ===== */
.info-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.info-card {
    position: relative; padding: 36px; background: var(--bg-card);
    border: 1px solid var(--border); border-radius: var(--radius);
    transition: all 0.4s; overflow: hidden;
    box-shadow: var(--shadow); backdrop-filter: blur(8px);
}
.info-card:hover { transform: translateY(-6px); border-color: var(--accent-1); box-shadow: 0 12px 40px rgba(99, 102, 241, 0.18); }
.card-glow {
    position: absolute; top: -50%; left: -50%; width: 200%; height: 200%;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.08) 0%, transparent 60%);
    opacity: 0; transition: opacity 0.4s;
}
.info-card:hover .card-glow { opacity: 1; }
.card-icon { font-size: 2.5rem; margin-bottom: 16px; }
.card-title { font-size: 1.3rem; font-weight: 700; margin-bottom: 12px; color: var(--text-primary); }
.card-desc { font-size: 0.9rem; color: var(--text-secondary); margin-bottom: 16px; line-height: 1.6; }
.card-formula {
    font-family: var(--mono); font-size: 0.78rem; padding: 12px 16px;
    background: rgba(99, 102, 241, 0.06); border-radius: 8px; color: var(--accent-3);
    margin-bottom: 16px; overflow-x: auto;
    border: 1px solid rgba(99, 102, 241, 0.1);
}
.card-tags { display: flex; gap: 8px; flex-wrap: wrap; }
.tag {
    padding: 4px 12px; font-size: 0.72rem; border-radius: 12px;
    background: rgba(99, 102, 241, 0.1); color: var(--accent-3);
    border: 1px solid rgba(99, 102, 241, 0.2);
}

/* ===== Pros & Cons ===== */
.proscons-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.proscons-card {
    padding: 36px; background: var(--bg-card); border-radius: var(--radius);
    border: 1px solid var(--border); box-shadow: var(--shadow);
    backdrop-filter: blur(8px);
}
.proscons-title { font-size: 1.3rem; font-weight: 700; margin-bottom: 24px; color: var(--text-primary); }
.proscons-list { list-style: none; }
.proscons-list li {
    display: flex; gap: 14px; padding: 16px 0;
    border-bottom: 1px solid rgba(99, 102, 241, 0.08);
}
.proscons-list li:last-child { border-bottom: none; }
.proscons-icon { font-size: 1.3rem; flex-shrink: 0; margin-top: 2px; }
.proscons-list strong { display: block; margin-bottom: 4px; font-size: 0.95rem; color: var(--text-primary); }
.proscons-list p { font-size: 0.85rem; color: var(--text-secondary); margin: 0; }

/* ===== Modal ===== */
.modal-overlay {
    position: fixed; inset: 0; z-index: 100;
    background: rgba(30, 27, 75, 0.4); backdrop-filter: blur(8px);
    display: flex; align-items: center; justify-content: center;
    opacity: 0; pointer-events: none; transition: opacity 0.3s;
}
.modal-overlay.open { opacity: 1; pointer-events: all; }
.modal-card {
    background: var(--bg-primary); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 40px; max-width: 500px;
    width: 90%; position: relative; transform: scale(0.9);
    transition: transform 0.3s; box-shadow: 0 24px 48px rgba(99, 102, 241, 0.15);
}
.modal-overlay.open .modal-card { transform: scale(1); }
.modal-close {
    position: absolute; top: 16px; right: 16px;
    background: none; border: none; color: var(--text-muted);
    font-size: 1.2rem; cursor: pointer; padding: 4px 8px;
}
.modal-icon { font-size: 3rem; margin-bottom: 16px; }
.modal-title { font-size: 1.4rem; font-weight: 700; margin-bottom: 12px; color: var(--text-primary); }
.modal-desc { color: var(--text-secondary); font-size: 0.95rem; line-height: 1.7; }

/* ===== Footer ===== */
.footer {
    position: relative; z-index: 1; padding: 40px 0;
    border-top: 1px solid var(--border); text-align: center;
    background: var(--bg-secondary);
}
.footer-content { display: flex; flex-direction: column; align-items: center; gap: 12px; }
.footer-brand { display: flex; align-items: center; gap: 10px; }
.footer-logo { font-size: 1.5rem; }
.footer-title { font-weight: 700; font-size: 1.1rem; color: var(--text-primary); }
.footer-text { color: var(--text-muted); font-size: 0.85rem; }
.footer-links { display: flex; gap: 20px; }
.footer-links a { color: var(--text-secondary); text-decoration: none; font-size: 0.85rem; transition: color 0.3s; }
.footer-links a:hover { color: var(--accent-3); }

/* ===== Animations ===== */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(24px); }
    to { opacity: 1; transform: translateY(0); }
}
@keyframes nodePulse {
    0% { opacity: 0.6; transform: translate(-50%, -50%) scale(1); box-shadow: 0 0 0 0 rgba(99, 102, 241, 0.4); }
    100% { opacity: 0; transform: translate(-50%, -50%) scale(1.5); box-shadow: 0 0 0 20px rgba(99, 102, 241, 0); }
}
@keyframes float { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-10px); } }

.fade-in { animation: fadeInUp 0.6s ease both; }

/* ===== Responsive ===== */
@media (max-width: 900px) {
    .demo-container { grid-template-columns: 1fr; }
    .info-grid { grid-template-columns: 1fr; }
    .proscons-grid { grid-template-columns: 1fr; }
    .formula-legend { grid-template-columns: 1fr; }
    .formula-fraction { font-size: 1.1rem; flex-wrap: wrap; justify-content: center; }
    .formula-card { padding: 28px; }
    .section { padding: 60px 0; }
}
@media (max-width: 600px) {
    .hero-title { font-size: 2rem; }
    .arch-nodes { gap: 10px; }
    .arch-node { min-width: 100px; padding: 14px 12px; }
}