/* CSZ Digital inspired - Black & White minimal */
:root {
    --bg-primary: #000000;
    --bg-secondary: #0a0a0a;
    --bg-tertiary: #111111;
    --white: #ffffff;
    --white-dim: #e0e0e0;
    --gray: #888888;
    --gray-dark: #333333;
    --border: #ffffff;
    --border-dim: #444444;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-primary);
    color: var(--white);
    line-height: 1.7;
    min-height: 100vh;
}

.container {
    max-width: 860px;
    margin: 0 auto;
    padding: 3rem 1.5rem;
}

/* Header */
.header {
    text-align: center;
    margin-bottom: 4rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--border-dim);
}

.header h1 {
    font-size: 2.75rem;
    font-weight: 300;
    color: var(--white);
    margin-bottom: 0.75rem;
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.subtitle {
    font-size: 1rem;
    color: var(--gray);
    font-weight: 400;
    letter-spacing: 0.05em;
}

/* Video section */
.video-section {
    margin-bottom: 4rem;
}

.video-container {
    position: relative;
    width: 100%;
    aspect-ratio: 16 / 9;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    overflow: hidden;
}

.video-container video {
    width: 100%;
    height: 100%;
    display: block;
    object-fit: contain;
    background: #000;
}

/* Video placeholder when no source */
.video-placeholder {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    color: var(--gray);
    text-align: center;
    padding: 2rem;
}

.video-placeholder svg {
    width: 48px;
    height: 48px;
    margin-bottom: 1rem;
    opacity: 0.5;
}

.video-placeholder p {
    font-size: 0.9rem;
}

.video-container:has(video[src]:not([src=""])) .video-placeholder {
    display: none;
}

.video-controls {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    margin-top: 1.5rem;
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-dim);
}

.video-controls label {
    font-size: 0.8rem;
    color: var(--gray);
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.speed-buttons {
    display: flex;
    gap: 0.5rem;
}

/* CSZ-style buttons - minimal with white border */
.btn {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--white);
    padding: 0.5rem 1rem;
    font-size: 0.8rem;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: 'Inter', sans-serif;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.btn:hover {
    background: var(--white);
    color: var(--bg-primary);
}

.btn.active {
    background: var(--white);
    color: var(--bg-primary);
}

.speed-btn {
    background: transparent;
    border: 1px solid var(--border-dim);
    color: var(--gray);
    padding: 0.4rem 0.75rem;
    font-size: 0.75rem;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: 'Inter', sans-serif;
}

.speed-btn:hover {
    border-color: var(--white);
    color: var(--white);
}

.speed-btn.active {
    background: var(--white);
    border-color: var(--white);
    color: var(--bg-primary);
}

/* Math explanation section */
.explanation {
    margin-bottom: 4rem;
}

.explanation h2 {
    font-size: 1.5rem;
    font-weight: 300;
    color: var(--white);
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-dim);
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.math-section {
    margin-bottom: 3rem;
}

.math-section h3 {
    font-size: 1rem;
    font-weight: 500;
    color: var(--white);
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.math-section p {
    font-size: 0.95rem;
    color: var(--white-dim);
    margin-bottom: 1rem;
    line-height: 1.8;
}

.math-section ul {
    list-style: none;
    margin: 1rem 0;
}

.math-section li {
    font-size: 0.9rem;
    color: var(--white-dim);
    padding: 0.5rem 0;
    padding-left: 1.5rem;
    position: relative;
}

.math-section li::before {
    content: "—";
    position: absolute;
    left: 0;
    color: var(--gray);
}

.equation {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1rem;
    color: var(--white);
    background: var(--bg-secondary);
    padding: 1.25rem 1.5rem;
    margin: 1.5rem 0;
    border-left: 2px solid var(--white);
    overflow-x: auto;
}

.equation-label {
    font-size: 0.75rem;
    color: var(--gray);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 0.5rem;
    display: block;
}

.note {
    font-size: 0.85rem;
    color: var(--gray);
    font-style: italic;
    margin-top: 0.5rem;
}

.math-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin: 1.5rem 0;
}

.math-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-dim);
    padding: 1.25rem;
}

.math-card h4 {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--gray);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.75rem;
}

.math-card .value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.1rem;
    color: var(--white);
}

/* Code section */
.code-section {
    margin-bottom: 4rem;
}

.code-toggle {
    width: 100%;
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.5rem;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--white);
    font-size: 0.85rem;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: 'Inter', sans-serif;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.code-toggle:hover {
    background: var(--white);
    color: var(--bg-primary);
}

.code-toggle.active {
    background: var(--white);
    color: var(--bg-primary);
    border-bottom: none;
}

.python-icon {
    width: 20px;
    height: 20px;
}

.chevron {
    margin-left: auto;
    transition: transform 0.3s ease;
    width: 16px;
    height: 16px;
}

.code-toggle.active .chevron {
    transform: rotate(180deg);
}

.code-panel {
    display: none;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-top: none;
}

.code-panel.open {
    display: block;
}

.code-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1.25rem;
    border-bottom: 1px solid var(--border-dim);
}

.filename {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    color: var(--gray);
}

.copy-btn {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--white);
    padding: 0.35rem 0.75rem;
    font-size: 0.7rem;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: 'Inter', sans-serif;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.copy-btn:hover {
    background: var(--white);
    color: var(--bg-primary);
}

.copy-btn.copied {
    background: var(--white);
    color: var(--bg-primary);
}

.code-panel pre {
    margin: 0;
    padding: 1.5rem;
    overflow-x: auto;
    max-height: 500px;
    overflow-y: auto;
}

.code-panel code {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.8rem;
    line-height: 1.7;
}

/* Prism overrides for B&W */
.code-panel pre[class*="language-"],
.code-panel code[class*="language-"] {
    background: transparent;
    color: var(--white-dim);
}

.token.comment { color: #666; }
.token.keyword { color: #fff; font-weight: 500; }
.token.string { color: #aaa; }
.token.number { color: #fff; }
.token.function { color: #ccc; }
.token.class-name { color: #fff; }
.token.operator { color: #888; }
.token.punctuation { color: #666; }

/* Footer */
.footer {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid var(--border-dim);
}

.footer p {
    font-size: 0.8rem;
    color: var(--gray);
    letter-spacing: 0.05em;
}

.footer a {
    color: var(--white);
    text-decoration: none;
    border-bottom: 1px solid var(--border-dim);
    transition: border-color 0.2s ease;
}

.footer a:hover {
    border-color: var(--white);
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--border-dim);
}

::-webkit-scrollbar-thumb:hover {
    background: var(--gray);
}

/* Responsive */
@media (max-width: 640px) {
    .container {
        padding: 2rem 1rem;
    }

    .header h1 {
        font-size: 1.75rem;
    }

    .video-controls {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }

    .speed-buttons {
        flex-wrap: wrap;
    }

    .equation {
        font-size: 0.85rem;
        padding: 1rem;
    }
}