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

:root {
    --color-bg: #f4f7fb;
    --color-surface: #ffffff;
    --color-surface-soft: #f8fbff;
    --color-surface-alt: linear-gradient(180deg, #fbfdff 0%, #f6faff 100%);
    --color-primary: #4576df;
    --color-primary-dark: #243b86;
    --color-success: #16a34a;
    --color-warning: #f59e0b;
    --color-danger: #ef444470;
    --color-text: #1f2937;
    --color-muted: #6b7280;
    --color-border: #dbe3ef;
    --color-node: #dbeafe;
    --color-node-border: #3b82f6;
    --color-node-active: #fef3c7;
    --color-node-visited: #dcfce7;
    --color-node-end: #fce7f3;
    --color-node-end-border: #db2777;
    --color-edge: #8aa3c7;
    --color-edge-active: #2563eb;
    --color-edge-route: #16a34a;
    --shadow-main: 0 12px 30px rgba(15, 23, 42, 0.08);
    --radius-lg: 20px;
    --radius-md: 16px;
    --radius-sm: 12px;
    --transition-fast: 0.25s ease;
}

body {
    font-family: "Poppins", sans-serif;
    background: linear-gradient(180deg, #eef4ff 0%, #f8fbff 40%, var(--color-bg) 100%);
    color: var(--color-text);
    line-height: 1.7;
}

.container {
    width: min(1150px, 92%);
    margin: 0 auto;
}

/* HERO */
.hero {
    background: linear-gradient(135deg, rgba(37, 99, 235, 0.96), rgba(20, 184, 166, 0.9));
    color: #fff;
    padding: 88px 0 72px;
    text-align: center;
    box-shadow: var(--shadow-main);
}

.eyebrow {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 9px 16px;
    margin-bottom: 20px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.14);
    font-size: 0.95rem;
    backdrop-filter: blur(10px);
}

.hero h1 {
    margin-bottom: 18px;
    font-size: clamp(2rem, 4vw, 3.4rem);
    line-height: 1.15;
    font-weight: 700;
}

.hero-text {
    max-width: 860px;
    margin: 0 auto;
    font-size: 1.05rem;
    color: rgba(255, 255, 255, 0.95);
}

/* MAIN */
main {
    padding: 52px 0 80px;
}

/* PANELS/CARDS */
.card,
.panel,
.feature-box,
.distance-row,
.process-list li {
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-main);
}

.card {
    margin-bottom: 28px;
    padding: 32px;
    border-radius: var(--radius-lg);
    background: var(--color-surface);
}

.card h2 {
    margin-bottom: 14px;
    font-size: 1.65rem;
    color: var(--color-primary-dark);
}

.card h3 {
    margin-bottom: 8px;
    font-size: 1.08rem;
}

.card p {
    margin-bottom: 14px;
}

.card ul,
.card ol {
    padding-left: 22px;
    margin-top: 10px;
}

.card li {
    margin-bottom: 8px;
}

strong {
    color: var(--color-primary-dark);
}

.panel {
    padding: 20px;
    border-radius: var(--radius-lg);
    background: var(--color-surface-alt);
}

.panel-header {
    margin-bottom: 14px;
}

.panel-header h3 {
    margin-bottom: 4px;
    color: var(--color-primary-dark);
}

.panel-header p {
    margin-bottom: 0;
    color: var(--color-muted);
    font-size: 0.95rem;
}

/* GRIDS */
.feature-grid,
.split-grid,
.interactive-demo {
    display: grid;
    gap: 22px;
}

.feature-grid {
    grid-template-columns: repeat(3, 1fr);
    margin: 22px 0;
}

.split-grid {
    grid-template-columns: repeat(2, 1fr);
    margin-top: 20px;
}

.interactive-demo {
    grid-template-columns: 1.5fr 0.9fr;
    align-items: start;
    margin-top: 20px;
}

.algorithm-foundation {
    margin: 20px 0 14px;
}

.foundation-note {
    margin-top: 2px;
    padding: 14px 16px;
    border: 1px solid #cfe0ff;
    border-radius: var(--radius-sm);
    background: #eef4ff;
    color: var(--color-primary-dark);
    font-weight: 500;
}

/* FEATURE BOXES */
.feature-box {
    padding: 24px 18px;
    border-radius: var(--radius-md);
    background: var(--color-surface-soft);
    text-align: center;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.feature-box:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 22px rgba(37, 99, 235, 0.12);
}

.feature-box i {
    margin-bottom: 12px;
    font-size: 1.75rem;
    color: var(--color-primary);
}

.feature-box p {
    margin-bottom: 0;
    color: var(--color-muted);
}

/* SVG */
.svg-shell {
    padding: 10px;
    overflow: hidden;
    border: 1px solid #e2e8f0;
    border-radius: var(--radius-md);
    background: linear-gradient(180deg, #fdfefe 0%, #f3f8ff 100%);
}

.def {
    display: inline-block;
    align-items: center;
    margin-right: 25px;
}

.graph-svg {
    display: block;
    width: 100%;
    height: auto;
}

/* EDGES */
.edge {
    stroke: var(--color-edge);
    stroke-width: 6;
    stroke-linecap: round;
}

.edge-active {
    stroke: var(--color-edge-active);
    stroke-width: 8;
}

.edge-route {
    stroke: var(--color-edge-route);
    stroke-width: 8;
}

.edge-faded {
    opacity: 0.25;
}

/* NODES */
.node {
    fill: var(--color-node);
    stroke: var(--color-node-border);
    stroke-width: 4;
}

.node-start {
    fill: var(--color-node-visited);
    stroke: var(--color-success);
}

.node-end {
    fill: var(--color-node-end);
    stroke: var(--color-node-end-border);
}

.node-current {
    fill: var(--color-node-active);
    stroke: var(--color-warning);
}

.node-visited {
    fill: var(--color-node-visited);
    stroke: var(--color-success);
}

.node-route {
    fill: var(--color-node-visited);
    stroke: var(--color-success);
}

.node-label {
    fill: #0f172a;
    font-size: 1.2rem;
    font-weight: 700;
    text-anchor: middle;
    dominant-baseline: middle;
}

.node-label-sm {
    font-size: 1rem;
}

/* SVG LABELS */
.weight-label {
    fill: #1e3a8a;
    font-size: 1rem;
    font-weight: 700;
    text-anchor: middle;
}

.road-line {
    stroke: #94a3b8;
    stroke-width: 18;
    stroke-linecap: round;
}

.intersection {
    fill: var(--color-primary);
    stroke: #fff;
    stroke-width: 5;
}

.route-line {
    fill: none;
    stroke: var(--color-danger);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-linejoin: round;
    stroke-dasharray: 10 8;
}

.mini-label {
    fill: #1e293b;
    font-size: 1rem;
    font-weight: 700;
}

.diagram-label {
    fill: var(--color-primary-dark);
    font-size: 0.95rem;
    font-weight: 600;
}

.label-line {
    stroke: var(--color-primary-dark);
    stroke-width: 2.5;
    stroke-linecap: round;
}

/* LEGEND */
.legend {
    display: flex;
    flex-wrap: wrap;
    gap: 18px;
    margin-top: 16px;
    color: var(--color-muted);
    font-size: 0.95rem;
}

.legend span {
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.legend-dot {
    display: inline-block;
    width: 14px;
    height: 14px;
    border-radius: 50%;
}

.legend-default {
    background: var(--color-node);
}

.legend-line {
    display: inline-block;
    width: 22px;
    height: 4px;
    border-radius: 999px;
    background: var(--color-edge);
}

.legend-weight {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: #eef4ff;
    color: var(--color-primary-dark);
    font-size: 0.85rem;
    font-weight: 700;
    border: 1px solid #cfe0ff;
}

.distance-table {
    display: grid;
    gap: 10px;
    margin-top: 18px;
}

.distance-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 14px;
    border-radius: var(--radius-sm);
    background: var(--color-surface);
}

.distance-row span {
    font-weight: 600;
}

.distance-row strong {
    color: var(--color-primary);
    font-size: 1rem;
}

/* DEMOS */
.demo-controls {
    display: flex;
    gap: 12px;
    margin-top: 20px;
}

.demo-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 18px;
    border: none;
    border-radius: var(--radius-sm);
    font-family: inherit;
    font-size: 0.96rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease, opacity 0.2s ease, background 0.2s ease;
}

.demo-btn:hover {
    transform: translateY(-2px);
}

.demo-btn:disabled {
    opacity: 0.45;
    cursor: not-allowed;
    transform: none;
}

.demo-btn-primary {
    background: var(--color-primary);
    color: #fff;
}

.demo-btn-secondary {
    background: #eaf1ff;
    color: var(--color-primary-dark);
}

/* SVG FORMATTING */
.distance-box {
    fill: #fff;
    stroke: #cbd5e1;
    stroke-width: 2;
}

.distance-text {
    fill: var(--color-primary-dark);
    font-size: 1rem;
    font-weight: 700;
    text-anchor: middle;
}

.process-list {
    display: grid;
    gap: 10px;
}

.process-list li {
    padding: 14px 16px;
    border-radius: var(--radius-sm);
    background: var(--color-surface-soft);
    list-style-position: inside;
}

/* MISC */
.step-badge {
    display: inline-block;
    padding: 8px 14px;
    margin-bottom: 14px;
    border-radius: 999px;
    background: var(--color-primary);
    color: #fff;
    font-size: 0.9rem;
    font-weight: 600;
}

.result-note {
    margin-top: 14px;
    padding: 12px 14px;
    border: 1px solid #bbf7d0;
    border-radius: var(--radius-sm);
    background: #ecfdf5;
    color: #166534;
    font-weight: 500;
}

.conclusion {
    border-left: 6px solid var(--color-primary);
    background: linear-gradient(180deg, #ffffff 0%, #f8fbff 100%);
}

.references-list {
    margin-top: 10px;
    padding-left: 20px;
}

.references-list li {
    margin-bottom: 8px;
    line-height: 1.5;
}

/* UI */
@media (max-width: 980px) {
    .feature-grid,
    .split-grid,
    .interactive-demo {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 640px) {
    .hero {
        padding: 68px 0 54px;
    }

    .card {
        padding: 22px 18px;
    }

    .demo-controls {
        flex-direction: column;
    }

    .hero-text {
        font-size: 0.98rem;
    }

    .card h2 {
        font-size: 1.35rem;
    }
}