:root {
    --bg: #f8f9fa;
    --text: #1a1a1a;
    --accent: #2c3e50;
    --card-bg: #ffffff;
    --border: #e1e4e8;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg);
    color: var(--text);
    line-height: 1.6;
    margin: 0;
    padding-bottom: 3rem;
}

.container { max-width: 850px; margin: 0 auto; padding: 2rem; }

header { border-bottom: 1px solid var(--border); background: white; padding: 2.5rem 0; }
header h1 { font-weight: 300; letter-spacing: -2px; margin-bottom: 0; font-size: 2.5rem; color: var(--accent); }
.subtitle { color: #666; font-size: 0.8rem; margin-top: 5px; text-transform: uppercase; letter-spacing: 2px; }

.section-title { 
    font-size: 0.75rem; 
    text-transform: uppercase; 
    color: #95a5a6; 
    letter-spacing: 2.5px; 
    margin-top: 4rem; 
    margin-bottom: 1.5rem;
    border-bottom: 1px solid var(--border);
    padding-bottom: 10px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    list-style: none;
    user-select: none;
}

.section-title::-webkit-details-marker { display: none; }

.section-title::after {
    content: '+';
    font-size: 1.2rem;
    font-weight: 300;
    color: var(--accent);
    transition: transform 0.2s ease;
}

details[open] .section-title::after {
    content: '−';
}

details[open] .section-title {
    margin-bottom: 1.5rem;
}

details summary:focus { outline: none; }

.card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: 1.8rem;
    border-radius: 8px;
    display: block;
    text-decoration: none;
    color: inherit;
    transition: all 0.25s ease;
    box-shadow: var(--shadow);
}

.card:hover { border-color: var(--accent); transform: translateY(-3px); }

.card.active { border-left: 6px solid var(--accent); display: flex; justify-content: space-between; align-items: center; }

.topic { font-size: 1.2rem; font-weight: 600; color: var(--accent); }

.resource-card { display: flex; flex-direction: column; justify-content: space-between; position: relative; }
.resource-card .status-badge { position: absolute; top: 1.8rem; right: 1.8rem; }
.resource-card h3 { margin-right: 5rem; }

.status-badge { 
    background: #ecf0f1; 
    padding: 6px 14px; 
    border-radius: 20px; 
    font-family: 'JetBrains Mono', monospace; 
    font-size: 0.7rem; 
    color: #34495e;
    text-transform: uppercase;
}

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 1.5rem; }

.history-card h3 { margin: 10px 0 5px 0; font-size: 1.1rem; }
.history-card p { font-size: 0.9rem; color: #7f8c8d; margin: 0; }

.resource .icon { font-size: 1.5rem; margin-bottom: 15px; }

.section-header { display: flex; justify-content: space-between; align-items: flex-end; }
.controls button {
    background: white;
    border: 1px solid var(--border);
    padding: 6px 12px;
    border-radius: 4px;
    font-size: 0.75rem;
    cursor: pointer;
    margin-left: 5px;
    color: var(--accent);
}
.controls button:hover { background: #f0f0f0; }

.search-box { margin-bottom: 2rem; }
.search-box input {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    box-sizing: border-box;
}

.glossary-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 1rem; }
.glossary-item {
    background: white;
    border: 1px solid var(--border);
    padding: 1rem;
    border-radius: 6px;
}
.glossary-item .term { font-size: 1rem; border-bottom: 1px solid #f0f0f0; padding-bottom: 5px; margin-bottom: 5px; }
.glossary-item .term small { color: #888; display: block; font-size: 0.7rem; }
.glossary-item .definition { font-size: 0.85rem; color: #444; }
.glossary-item .backlink { font-size: 0.7rem; margin-top: 10px; color: #999; }
.glossary-item .backlink a { color: var(--accent); text-decoration: none; }

footer { margin-top: 5rem; text-align: center; border-top: 1px solid var(--border); padding-top: 2rem; color: #95a5a6; font-size: 0.8rem; }

/* Mobile Responsiveness */
@media (max-width: 600px) {
    .container { padding: 1.5rem; }
    header h1 { font-size: 2rem; }
    .card.active { flex-direction: column; align-items: flex-start; gap: 10px; }
}

/* Page Content (Classes) */
.lesson-content { background: white; padding: 3rem; border-radius: 8px; border: 1px solid var(--border); margin-top: 2rem; }
.lesson-content h2 { margin-top: 2rem; color: var(--accent); border: none; padding: 0; font-size: 1.5rem; }
.lesson-content ul { padding-left: 20px; }
.lesson-content li { margin-bottom: 8px; }
.lesson-content code { background: #f0f0f0; padding: 2px 6px; border-radius: 4px; font-family: 'JetBrains Mono', monospace; }