/* iff — ifandonlyif.xyz */
:root {
    --bg: #0a0a0a;
    --bg-raised: #141414;
    --bg-card: #1a1a1a;
    --border: #2a2a2a;
    --text: #e8e8e8;
    --text-muted: #888;
    --accent: #7eb8da;
    --accent-dim: #4a7a94;
    --code-bg: #1e1e2e;
    --serif: 'EB Garamond', Georgia, serif;
    --sans: 'Inter', -apple-system, sans-serif;
    --mono: 'JetBrains Mono', 'Fira Code', monospace;
}

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

body {
    font-family: var(--sans);
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

code {
    font-family: var(--mono);
    font-size: 0.9em;
    background: var(--code-bg);
    padding: 0.15em 0.4em;
    border-radius: 4px;
}

/* Nav */
nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 2rem;
    max-width: 1100px;
    margin: 0 auto;
}

.logo {
    font-family: var(--mono);
    font-size: 1.2rem;
    font-weight: 500;
    color: var(--text);
}
.logo:hover { text-decoration: none; color: var(--accent); }

.nav-links { display: flex; gap: 2rem; }
.nav-links a { color: var(--text-muted); font-size: 0.9rem; }
.nav-links a:hover { color: var(--text); text-decoration: none; }

/* Hero */
.hero {
    text-align: center;
    padding: 6rem 2rem 4rem;
    max-width: 800px;
    margin: 0 auto;
}

.hero-tag {
    font-family: var(--mono);
    font-size: 0.85rem;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.15em;
    margin-bottom: 1.5rem;
}

.hero h1 {
    font-family: var(--serif);
    font-size: 3.5rem;
    font-weight: 400;
    line-height: 1.2;
    margin-bottom: 1.5rem;
}

.hero-sub {
    font-size: 1.15rem;
    color: var(--text-muted);
    max-width: 550px;
    margin: 0 auto 2.5rem;
    line-height: 1.7;
}

.hero-actions { display: flex; gap: 1rem; justify-content: center; }

.btn {
    display: inline-block;
    padding: 0.75rem 1.75rem;
    border-radius: 6px;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.2s;
}
.btn:hover { text-decoration: none; }

.btn-primary {
    background: var(--accent);
    color: var(--bg);
}
.btn-primary:hover { background: #9ccae6; }

.btn-secondary {
    border: 1px solid var(--border);
    color: var(--text-muted);
}
.btn-secondary:hover { border-color: var(--text-muted); color: var(--text); }

/* Sections */
section {
    max-width: 1000px;
    margin: 0 auto;
    padding: 4rem 2rem;
}

section h2 {
    font-family: var(--serif);
    font-size: 2rem;
    font-weight: 400;
    margin-bottom: 0.5rem;
}

/* How it works */
.steps {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    margin-top: 2rem;
}

.step {
    padding: 1.5rem;
    border: 1px solid var(--border);
    border-radius: 8px;
}

.step-num {
    font-family: var(--mono);
    font-size: 0.8rem;
    color: var(--accent);
    margin-bottom: 0.75rem;
}

.step h3 {
    font-size: 1rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.step p {
    font-size: 0.9rem;
    color: var(--text-muted);
    line-height: 1.6;
}

/* Tracks */
.tracks-intro {
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.track-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
}

.track-card {
    display: block;
    padding: 1.5rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--bg-raised);
    transition: all 0.2s;
    color: var(--text);
}
.track-card:hover { text-decoration: none; border-color: var(--accent-dim); }

.track-icon {
    font-family: var(--mono);
    font-size: 1.3rem;
    color: var(--accent);
    margin-bottom: 1rem;
}

.track-card h3 {
    font-size: 1.1rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.track-card p {
    font-size: 0.85rem;
    color: var(--text-muted);
    line-height: 1.5;
    margin-bottom: 1rem;
}

.track-status {
    font-family: var(--mono);
    font-size: 0.75rem;
    color: var(--accent);
}

.track-coming { opacity: 0.5; }
.track-coming:hover { opacity: 0.7; }
.track-coming .track-status { color: var(--text-muted); }

/* Prerequisites */
.prereq-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    margin-top: 2rem;
}

.prereq h3 {
    font-size: 1rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.prereq p {
    font-size: 0.9rem;
    color: var(--text-muted);
    line-height: 1.6;
}

/* Footer */
footer {
    text-align: center;
    padding: 3rem 2rem;
    border-top: 1px solid var(--border);
    max-width: 1000px;
    margin: 2rem auto 0;
}

footer p { font-size: 0.9rem; color: var(--text-muted); }
.footer-sub { margin-top: 0.5rem; font-size: 0.8rem; }

/* Exercise pages */
.exercise-page {
    max-width: 750px;
    margin: 0 auto;
    padding: 2rem;
}

.exercise-page h1 {
    font-family: var(--serif);
    font-size: 2.2rem;
    font-weight: 400;
    margin: 2rem 0 1rem;
}

.exercise-page h2 {
    font-family: var(--serif);
    font-size: 1.5rem;
    font-weight: 400;
    margin: 2rem 0 0.75rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border);
}

.exercise-page p {
    color: var(--text-muted);
    line-height: 1.8;
    margin-bottom: 1rem;
}

.exercise-page strong { color: var(--text); }

.breadcrumb {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 0.5rem;
}

.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--accent); }

pre {
    background: var(--code-bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.25rem;
    overflow-x: auto;
    margin: 1rem 0;
    font-family: var(--mono);
    font-size: 0.85rem;
    line-height: 1.7;
}

.exercise-nav {
    display: flex;
    justify-content: space-between;
    margin-top: 3rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border);
}

.exercise-nav a {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.hint {
    border: 1px solid var(--border);
    border-radius: 8px;
    margin: 1rem 0;
}

.hint summary {
    padding: 0.75rem 1rem;
    cursor: pointer;
    font-size: 0.9rem;
    color: var(--accent);
    font-family: var(--mono);
}

.hint-content {
    padding: 0 1rem 1rem;
    font-size: 0.9rem;
    color: var(--text-muted);
}

/* Track index */
.track-page {
    max-width: 750px;
    margin: 0 auto;
    padding: 2rem;
}

.track-page h1 {
    font-family: var(--serif);
    font-size: 2.5rem;
    font-weight: 400;
    margin: 2rem 0 0.5rem;
}

.track-page .track-desc {
    color: var(--text-muted);
    margin-bottom: 2rem;
    line-height: 1.7;
}

.exercise-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.exercise-list a {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.25rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--bg-raised);
    color: var(--text);
    transition: all 0.2s;
}
.exercise-list a:hover { text-decoration: none; border-color: var(--accent-dim); }

.ex-num {
    font-family: var(--mono);
    font-size: 0.8rem;
    color: var(--accent);
    min-width: 2rem;
}

.ex-title { font-weight: 500; }

.ex-difficulty {
    margin-left: auto;
    font-family: var(--mono);
    font-size: 0.75rem;
    color: var(--text-muted);
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 { font-size: 2.5rem; }
    .steps, .track-grid, .prereq-grid {
        grid-template-columns: 1fr;
    }
    .nav-links { gap: 1rem; }
    .hero-actions { flex-direction: column; align-items: center; }
}