/* Brain Teasers Sprint — solo-use flashcard flow. Emerald design system,
   readable in light + dark, clean on mobile. Tokens are defined locally so the
   page works standalone (it does not link design-system.css). */

:root {
    --bts-bg: #f8f5f0;
    --bts-surface: #ffffff;
    --bts-surface2: #fafbfc;
    --bts-border: #e5e7eb;
    --bts-border-strong: #d1d5db;
    --bts-text: #0f172a;
    --bts-dim: #4b5563;
    --bts-faint: #6b7280;
    --bts-accent: #059669;
    --bts-accent-bright: #10b981;
    --bts-accent-deep: #047857;
    --bts-accent-dim: rgba(16, 185, 129, 0.12);
    --bts-good: #059669;
    --bts-good-deep: #047857;
    --bts-good-bg: #ecfdf5;
    --bts-good-border: #10b981;
    --bts-good-text: #064e3b;
    --bts-bad-bg: #fef2f2;
    --bts-bad-text: #991b1b;
    --bts-warn-bg: #fffbeb;
    --bts-warn-border: #f59e0b;
    --bts-warn-text: #78350f;
    --bts-pill-bg: rgba(16, 185, 129, 0.14);
    --bts-pill-text: #047857;
    --bts-shadow: 0 2px 8px rgba(15, 23, 42, 0.05);
}

@media (prefers-color-scheme: dark) {
    :root {
        --bts-bg: #081210;
        --bts-surface: #0f1f1a;
        --bts-surface2: #15291f;
        --bts-border: rgba(255, 255, 255, 0.10);
        --bts-border-strong: rgba(255, 255, 255, 0.18);
        --bts-text: #eef2ff;
        --bts-dim: #9aa6c4;
        --bts-faint: #6b7799;
        --bts-accent: #10b981;
        --bts-accent-bright: #34d399;
        --bts-accent-deep: #0a7f5b;
        --bts-accent-dim: rgba(16, 185, 129, 0.16);
        --bts-good: #10b981;
        --bts-good-deep: #0a7f5b;
        --bts-good-bg: rgba(16, 185, 129, 0.14);
        --bts-good-border: #34d399;
        --bts-good-text: #a7f3d0;
        --bts-bad-bg: rgba(251, 113, 133, 0.14);
        --bts-bad-text: #fda4af;
        --bts-warn-bg: rgba(245, 158, 11, 0.13);
        --bts-warn-border: #f59e0b;
        --bts-warn-text: #fcd34d;
        --bts-pill-bg: rgba(45, 212, 191, 0.16);
        --bts-pill-text: #5eead4;
        --bts-shadow: 0 10px 26px rgba(0, 0, 0, 0.35);
    }
}

body {
    background: var(--bts-bg);
    color: var(--bts-text);
}

.bts-container {
    max-width: 760px;
    margin: 60px auto 80px;
    padding: 0 20px;
    font-family: 'Inter', system-ui, sans-serif;
    color: var(--bts-text);
}

.bts-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    gap: 16px;
    margin-bottom: 24px;
}

.bts-header h1 { margin: 0 0 4px; font-size: 1.85em; }
.bts-subtitle { margin: 0; color: var(--bts-faint); font-size: 0.95em; }

.bts-elapsed {
    font-variant-numeric: tabular-nums;
    font-weight: 600;
    font-size: 1.3em;
    color: var(--bts-dim);
    padding: 6px 12px;
    background: var(--bts-surface2);
    border: 1px solid var(--bts-border);
    border-radius: 8px;
    min-width: 70px;
    text-align: center;
}

.bts-panel {
    background: var(--bts-surface);
    border: 1px solid var(--bts-border);
    border-radius: 14px;
    padding: 22px 24px;
    box-shadow: var(--bts-shadow);
}

.bts-panel.hidden { display: none; }

.bts-instructions { color: var(--bts-dim); margin-bottom: 16px; line-height: 1.5; }

.bts-controls {
    display: flex;
    flex-wrap: wrap;
    gap: 16px;
    margin-bottom: 20px;
}

.bts-controls label {
    display: flex;
    flex-direction: column;
    gap: 6px;
    font-size: 0.9em;
    color: var(--bts-dim);
}

.bts-controls select {
    font: inherit;
    padding: 8px 12px;
    border: 1px solid var(--bts-border-strong);
    border-radius: 8px;
    background: var(--bts-surface);
    color: var(--bts-text);
    min-width: 200px;
    max-width: 100%;
}

.bts-hud {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 12px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--bts-border);
    margin-bottom: 18px;
    font-size: 0.95em;
    color: var(--bts-dim);
    flex-wrap: wrap;
}

.bts-hud strong { color: var(--bts-text); margin-right: 4px; }

.bts-meta-pill {
    background: var(--bts-pill-bg);
    color: var(--bts-pill-text);
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 0.85em;
    font-weight: 600;
}

.bts-card {
    background: var(--bts-surface2);
    border: 1px solid var(--bts-border);
    border-radius: 10px;
    padding: 18px 18px 14px;
    margin-bottom: 14px;
}

.bts-prompt {
    font-size: 1.1em;
    line-height: 1.55;
    color: var(--bts-text);
    white-space: pre-wrap;
    margin-bottom: 16px;
}

.bts-reveal { margin: 0; }

.bts-answer {
    margin-top: 14px;
    padding: 14px 16px;
    background: var(--bts-good-bg);
    border-left: 3px solid var(--bts-good-border);
    border-radius: 6px;
    color: var(--bts-good-text);
    font-size: 0.97em;
    line-height: 1.55;
    white-space: pre-wrap;
}

.bts-answer.hidden { display: none; }

.bts-actions {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    align-items: center;
    margin-bottom: 14px;
}

.bts-actions.hidden { display: none; }

.bts-actions .primary,
.bts-actions .secondary,
.bts-actions .bts-link {
    padding: 10px 18px;
    border-radius: 8px;
    font-weight: 600;
    text-decoration: none;
    border: none;
    cursor: pointer;
    font: inherit;
    font-weight: 600;
    font-size: 0.95em;
}

.bts-actions .primary { background: var(--bts-accent); color: #ffffff; }
.bts-actions .primary:hover { background: var(--bts-accent-deep); }
.bts-actions .primary:disabled { opacity: 0.55; cursor: default; }
.bts-actions .primary.good { background: var(--bts-good); }
.bts-actions .primary.good:hover { background: var(--bts-good-deep); }

.bts-actions .secondary {
    background: var(--bts-surface2);
    color: var(--bts-text);
    border: 1px solid var(--bts-border-strong);
}
.bts-actions .secondary:hover { border-color: var(--bts-accent); }
.bts-actions .secondary.bad { background: var(--bts-bad-bg); color: var(--bts-bad-text); border-color: transparent; }
.bts-actions .secondary.bad:hover { filter: brightness(0.97); }

.bts-actions .bts-link { color: var(--bts-accent); background: transparent; }
.bts-actions .bts-link:hover { text-decoration: underline; }

.bts-end-actions {
    display: flex;
    justify-content: space-between;
    margin-top: 8px;
    font-size: 0.9em;
    gap: 10px;
}

.bts-end-actions button {
    background: transparent;
    border: 1px solid var(--bts-border-strong);
    border-radius: 6px;
    padding: 6px 12px;
    cursor: pointer;
    color: var(--bts-dim);
    font: inherit;
    font-size: 0.9em;
}

.bts-end-actions button:hover { border-color: var(--bts-accent); color: var(--bts-text); }

/* ── LEARN block (shown after a miss) ───────────────────────────────── */
.bts-learn {
    margin-top: 14px;
    padding: 14px 16px;
    background: var(--bts-warn-bg);
    border-left: 3px solid var(--bts-warn-border);
    border-radius: 6px;
    color: var(--bts-warn-text);
    font-size: 0.95em;
    line-height: 1.5;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.bts-learn.hidden { display: none; }

.bts-learn-head { font-weight: 700; }

.bts-learn-link {
    color: var(--bts-accent-deep);
    font-weight: 600;
    text-decoration: none;
}
.bts-learn-link:hover { text-decoration: underline; }
@media (prefers-color-scheme: dark) {
    .bts-learn-link { color: var(--bts-accent-bright); }
}

.bts-copy-row {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 8px 12px;
}

.bts-copy-btn {
    background: var(--bts-accent);
    color: #ffffff;
    border: none;
    border-radius: 8px;
    padding: 8px 14px;
    font: inherit;
    font-weight: 600;
    font-size: 0.9em;
    cursor: pointer;
}
.bts-copy-btn:hover { background: var(--bts-accent-deep); }

.bts-copy-hint { color: var(--bts-dim); font-size: 0.85em; }

.bts-copy-fallback {
    width: 100%;
    min-height: 72px;
    margin-top: 4px;
    font: inherit;
    font-size: 0.85em;
    padding: 8px 10px;
    border: 1px solid var(--bts-border-strong);
    border-radius: 8px;
    background: var(--bts-surface);
    color: var(--bts-text);
    resize: vertical;
}

.bts-learn-next {
    align-self: flex-start;
    background: transparent;
    border: 1px solid var(--bts-border-strong);
    color: var(--bts-text);
    border-radius: 8px;
    padding: 8px 14px;
    font: inherit;
    font-weight: 600;
    font-size: 0.9em;
    cursor: pointer;
}
.bts-learn-next:hover { border-color: var(--bts-accent); }

.bts-broke-note { color: var(--bts-warn-text); font-weight: 600; }
.bts-broke-note a { color: var(--bts-accent-deep); }
@media (prefers-color-scheme: dark) {
    .bts-broke-note a { color: var(--bts-accent-bright); }
}

.bts-free-cue {
    color: var(--bts-good-deep);
    font-size: 0.88em;
    font-weight: 600;
}
@media (prefers-color-scheme: dark) {
    .bts-free-cue { color: var(--bts-good-border); }
}

/* ── Results ────────────────────────────────────────────────────────── */
.bts-result-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
    gap: 12px;
    margin: 18px 0 24px;
}

.bts-result-grid > div {
    background: var(--bts-surface2);
    border: 1px solid var(--bts-border);
    padding: 12px;
    border-radius: 8px;
    text-align: center;
    color: var(--bts-dim);
    font-size: 0.9em;
}

.bts-result-grid > div span { font-size: 1.4em; font-weight: 700; color: var(--bts-text); }

/* Tutorial CTA — inline below the revealed answer when a tag has a tutorial. */
.bts-tutorial-cta {
    margin-top: 14px;
    padding-top: 12px;
    border-top: 1px dashed var(--bts-border);
    font-size: 0.92em;
}
.bts-tutorial-link {
    color: var(--bts-accent);
    text-decoration: none;
    font-weight: 600;
}
.bts-tutorial-link:hover { text-decoration: underline; }

@media (max-width: 480px) {
    .bts-container { margin-top: 36px; padding: 0 14px; }
    .bts-prompt { font-size: 1em; }
    .bts-header { flex-direction: column; align-items: flex-start; gap: 10px; }
    .bts-controls select { min-width: 0; width: 100%; }
    .bts-actions .primary, .bts-actions .secondary { padding: 9px 14px; font-size: 0.9em; }
    .bts-copy-hint { width: 100%; }
}