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

:root {
    --bg: #0f1117;
    --bg-2: #1a1d27;
    --bg-3: #252938;
    --fg: #e8ecf4;
    --fg-dim: #9da7bd;
    --accent: #6c9eff;
    --accent-2: #8b5cf6;
    --success: #10b981;
    --danger: #ef4444;
    --warn: #f59e0b;
    --border: #2d3246;
    --radius: 14px;
    --shadow: 0 4px 20px rgba(0,0,0,.35);
}

html, body {
    margin: 0; padding: 0;
    height: 100%;
    background: var(--bg);
    color: var(--fg);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Inter, sans-serif;
    font-size: 15px; line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    overscroll-behavior: none;
}

#app {
    display: flex; flex-direction: column;
    min-height: 100vh; max-width: 780px;
    margin: 0 auto;
}

.topbar {
    position: sticky; top: 0; z-index: 10;
    display: flex; align-items: center; gap: 12px;
    padding: 12px 16px;
    background: linear-gradient(180deg, var(--bg-2) 0%, rgba(26,29,39,.85) 100%);
    backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--border);
}
.topbar h1 { margin: 0; font-size: 18px; font-weight: 600; flex: 1; }
.user-info { font-size: 12px; color: var(--fg-dim); text-align: right; }
.user-info b { color: var(--accent); font-weight: 600; }

.icon-btn {
    background: transparent; border: 0; color: var(--fg);
    font-size: 22px; padding: 4px 10px; cursor: pointer;
    border-radius: 8px;
}
.icon-btn:hover { background: var(--bg-3); }
.hidden { display: none !important; }

.main { flex: 1; padding: 16px 16px 90px; }
.loading { text-align: center; color: var(--fg-dim); padding: 40px 0; }

.tabbar {
    position: fixed; bottom: 0; left: 0; right: 0;
    display: flex; justify-content: space-around;
    background: var(--bg-2); border-top: 1px solid var(--border);
    padding: 6px 4px max(6px, env(safe-area-inset-bottom));
    max-width: 780px; margin: 0 auto;
}
.tab {
    flex: 1; background: transparent; border: 0; color: var(--fg-dim);
    display: flex; flex-direction: column; align-items: center; gap: 2px;
    padding: 8px 4px; font-size: 11px; cursor: pointer;
    border-radius: 10px;
}
.tab-icon { font-size: 22px; }
.tab.active { color: var(--accent); }

.card {
    background: var(--bg-2);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 16px; margin-bottom: 12px;
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: transform .1s, border-color .1s;
}
.card:hover, .card:active { border-color: var(--accent); transform: translateY(-1px); }
.card h3 { margin: 0 0 6px; font-size: 16px; font-weight: 600; }
.card .sub { color: var(--fg-dim); font-size: 13px; }

.level-card { display: flex; align-items: center; gap: 14px; }
.level-card .emoji { font-size: 32px; }
.level-card .info { flex: 1; }

.stat-grid {
    display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px;
    margin-bottom: 18px;
}
.stat {
    background: var(--bg-2); border: 1px solid var(--border);
    padding: 14px; border-radius: var(--radius);
}
.stat .label { color: var(--fg-dim); font-size: 12px; margin-bottom: 4px; }
.stat .value { font-size: 22px; font-weight: 700; color: var(--fg); }
.stat .value.accent { color: var(--accent); }
.stat .value.warn { color: var(--warn); }
.stat .value.success { color: var(--success); }

.progress-bar {
    background: var(--bg-3); height: 8px; border-radius: 999px;
    overflow: hidden; margin-top: 6px;
}
.progress-bar .fill {
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    height: 100%;
    transition: width .3s;
}

.lesson-content {
    background: var(--bg-2); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 16px; margin-bottom: 14px;
}
.lesson-content h2 { margin: 0 0 12px; font-size: 18px; }
.lesson-content code {
    background: #0a0b10; color: #a8e6ff;
    padding: 1px 5px; border-radius: 4px;
    font-size: 13px; font-family: "JetBrains Mono", "SF Mono", Consolas, monospace;
}
.lesson-content b { color: var(--fg); }
.lesson-content i { color: var(--fg-dim); }

.btn {
    display: block; width: 100%;
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-2) 100%);
    color: white; border: 0;
    padding: 14px; border-radius: var(--radius);
    font-size: 15px; font-weight: 600;
    cursor: pointer; margin-bottom: 8px;
    transition: opacity .15s;
}
.btn:hover { opacity: .92; }
.btn.secondary { background: var(--bg-3); color: var(--fg); }
.btn.success { background: var(--success); }
.btn.danger { background: var(--danger); }

.section-switch {
    display: flex; gap: 6px; margin-bottom: 14px;
    background: var(--bg-3); padding: 4px; border-radius: 12px;
}
.section-switch button {
    flex: 1; background: transparent; border: 0; color: var(--fg-dim);
    padding: 8px; border-radius: 9px; cursor: pointer; font-size: 13px;
}
.section-switch button.active {
    background: var(--bg-2); color: var(--fg); font-weight: 600;
}

.test-q { background: var(--bg-2); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; margin-bottom: 14px; }
.test-q .q { font-size: 15px; font-weight: 500; margin-bottom: 14px; }
.test-opt {
    display: block; width: 100%; text-align: left;
    background: var(--bg-3); border: 1px solid transparent;
    color: var(--fg); padding: 12px 14px;
    border-radius: 10px; font-size: 14px;
    cursor: pointer; margin-bottom: 8px;
}
.test-opt:hover { border-color: var(--accent); }
.test-opt.correct { background: rgba(16, 185, 129, .15); border-color: var(--success); }
.test-opt.wrong { background: rgba(239, 68, 68, .15); border-color: var(--danger); }

.result {
    padding: 16px; border-radius: var(--radius); margin-bottom: 14px;
    text-align: center; font-weight: 600;
}
.result.ok { background: rgba(16,185,129,.14); color: var(--success); }
.result.fail { background: rgba(239,68,68,.14); color: var(--danger); }

.ach-item {
    display: flex; align-items: center; gap: 12px;
    padding: 12px; background: var(--bg-2); border: 1px solid var(--border);
    border-radius: var(--radius); margin-bottom: 10px;
}
.ach-item.locked { opacity: .45; }
.ach-item .ach-ico { font-size: 26px; }

.lb-row {
    display: flex; align-items: center; gap: 12px;
    padding: 12px; background: var(--bg-2); border: 1px solid var(--border);
    border-radius: var(--radius); margin-bottom: 8px;
}
.lb-row .rank { font-size: 18px; font-weight: 700; width: 36px; text-align: center; color: var(--accent); }
.lb-row .name { flex: 1; }
.lb-row .pts { font-weight: 600; color: var(--warn); }

.empty {
    text-align: center; color: var(--fg-dim);
    padding: 40px 20px;
}
.empty .big { font-size: 48px; margin-bottom: 12px; }