*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}:root{--color-bg: #0f172a;--color-surface: #1e293b;--color-surface-2: #334155;--color-border: #475569;--color-text: #f1f5f9;--color-text-muted: #94a3b8;--color-primary: #6366f1;--color-primary-hover: #818cf8;--color-success: #22c55e;--color-danger: #ef4444;--color-warning: #f59e0b;--color-info: #3b82f6;--radius: 12px;--radius-sm: 8px;--max-width: 600px}html{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background:var(--color-bg);color:var(--color-text);-webkit-font-smoothing:antialiased}body{min-height:100dvh}#root{max-width:var(--max-width);margin:0 auto;padding:16px;min-height:100dvh}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:10px 20px;border:none;border-radius:var(--radius-sm);font-size:15px;font-weight:600;cursor:pointer;transition:background .15s,transform .1s;-webkit-tap-highlight-color:transparent}.btn:active{transform:scale(.97)}.btn-primary{background:var(--color-primary);color:#fff}.btn-primary:hover{background:var(--color-primary-hover)}.btn-secondary{background:var(--color-surface-2);color:var(--color-text)}.btn-secondary:hover{background:var(--color-border)}.btn-ghost{background:transparent;color:var(--color-text-muted)}.btn-ghost:hover{color:var(--color-text)}.btn-danger{background:var(--color-danger);color:#fff}.btn-lg{padding:14px 28px;font-size:17px}.app-header{display:flex;align-items:center;justify-content:space-between;padding:8px 0 24px}.app-header h1{font-size:24px;font-weight:700;letter-spacing:-.5px}.loading{display:flex;flex-direction:column;align-items:center;justify-content:center;min-height:60dvh;gap:16px;color:var(--color-text-muted)}.loading-spinner{width:36px;height:36px;border:3px solid var(--color-surface-2);border-top-color:var(--color-primary);border-radius:50%;animation:spin .8s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}.summary-cards{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-bottom:20px}.summary-card{background:var(--color-surface);border-radius:var(--radius);padding:16px 12px;text-align:center;display:flex;flex-direction:column;gap:4px}.summary-num{font-size:28px;font-weight:700;color:var(--color-primary)}.summary-label{font-size:12px;color:var(--color-text-muted);text-transform:uppercase;letter-spacing:.5px}.review-btn{width:100%;margin-bottom:24px}.concept-list h2{font-size:18px;margin-bottom:12px;color:var(--color-text-muted)}.concept-card{background:var(--color-surface);border-radius:var(--radius);padding:16px;margin-bottom:12px;display:flex;align-items:center;gap:12px;border-left:4px solid transparent}.concept-locked{opacity:.5;border-left-color:var(--color-border)}.concept-available{border-left-color:var(--color-info)}.concept-learning{border-left-color:var(--color-warning)}.concept-mastered{border-left-color:var(--color-success)}.concept-info{flex:1;min-width:0}.concept-header{display:flex;align-items:center;gap:8px;margin-bottom:4px}.concept-header h3{font-size:16px;font-weight:600}.concept-desc{font-size:13px;color:var(--color-text-muted);margin-bottom:8px}.status-badge{font-size:11px;padding:2px 8px;border-radius:100px;font-weight:600;text-transform:uppercase;letter-spacing:.5px;white-space:nowrap}.status-locked{background:var(--color-surface-2);color:var(--color-text-muted)}.status-available{background:#1e3a5f;color:var(--color-info)}.status-learning{background:#422006;color:var(--color-warning)}.status-mastered{background:#14532d;color:var(--color-success)}.concept-progress-bar{position:relative;height:6px;background:var(--color-surface-2);border-radius:3px;overflow:hidden;margin-top:4px}.concept-progress-fill{height:100%;background:var(--color-success);border-radius:3px;transition:width .3s ease}.concept-progress-text{font-size:11px;color:var(--color-text-muted);position:absolute;right:0;top:-16px}.study-view{display:flex;flex-direction:column;min-height:80dvh}.study-header{display:flex;align-items:center;gap:16px;padding-bottom:16px}.study-progress{flex:1;display:flex;align-items:center;gap:12px;font-size:14px;color:var(--color-text-muted)}.progress-bar{flex:1;height:6px;background:var(--color-surface-2);border-radius:3px;overflow:hidden}.progress-fill{height:100%;background:var(--color-primary);border-radius:3px;transition:width .3s ease}.flashcard{background:var(--color-surface);border-radius:var(--radius);padding:24px;flex:1;display:flex;flex-direction:column;gap:20px}.flashcard-question{text-align:center}.flashcard-question p{font-size:20px;font-weight:500;line-height:1.4}.hint-btn{background:none;border:none;color:var(--color-primary);font-size:13px;cursor:pointer;margin-top:8px;text-decoration:underline}.hint-text{font-size:14px;color:var(--color-text-muted);margin-top:8px;font-style:italic}.mc-options{display:grid;grid-template-columns:1fr 1fr;gap:10px}.mc-option{padding:14px 16px;background:var(--color-surface-2);border:2px solid transparent;border-radius:var(--radius-sm);color:var(--color-text);font-size:16px;font-weight:500;cursor:pointer;transition:border-color .15s,background .15s;-webkit-tap-highlight-color:transparent}.mc-option:hover{border-color:var(--color-primary);background:#2d3a52}.mc-option:active{transform:scale(.97)}.text-input-form{display:flex;gap:10px}.text-input-form input{flex:1;padding:12px 16px;border:2px solid var(--color-surface-2);border-radius:var(--radius-sm);background:var(--color-bg);color:var(--color-text);font-size:16px;outline:none;transition:border-color .15s}.text-input-form input:focus{border-color:var(--color-primary)}.flashcard-answer{display:flex;flex-direction:column;gap:12px;text-align:center}.answer-result{font-size:22px;font-weight:700;padding:8px;border-radius:var(--radius-sm)}.answer-result.correct{color:var(--color-success);background:#14532d40}.answer-result.incorrect{color:var(--color-danger);background:#7f1d1d40}.correct-answer,.your-answer{font-size:16px;color:var(--color-text-muted)}.rating-buttons{margin-top:8px}.rating-label{font-size:13px;color:var(--color-text-muted);margin-bottom:10px}.rating-row{display:grid;grid-template-columns:repeat(4,1fr);gap:8px}.rate-btn{display:flex;flex-direction:column;align-items:center;gap:2px;padding:12px 8px;border:2px solid var(--color-surface-2);border-radius:var(--radius-sm);background:var(--color-surface-2);color:var(--color-text);cursor:pointer;transition:border-color .15s,background .15s;-webkit-tap-highlight-color:transparent}.rate-btn:active{transform:scale(.95)}.rate-num{font-size:18px;font-weight:700}.rate-text{font-size:11px;color:var(--color-text-muted)}.rate-again{border-color:var(--color-danger)}.rate-again:hover{background:#7f1d1d40}.rate-hard{border-color:var(--color-warning)}.rate-hard:hover{background:#78350f40}.rate-good{border-color:var(--color-info)}.rate-good:hover{background:#1e3a5f40}.rate-easy{border-color:var(--color-success)}.rate-easy:hover{background:#14532d40}.study-complete{display:flex;flex-direction:column;align-items:center;justify-content:center;min-height:60dvh;gap:24px;text-align:center}.study-complete h2{font-size:24px}.session-stats{display:flex;flex-direction:column;align-items:center;gap:12px}.stat-circle{width:120px;height:120px;border-radius:50%;background:var(--color-surface);display:flex;flex-direction:column;align-items:center;justify-content:center;border:4px solid var(--color-primary)}.stat-pct{font-size:32px;font-weight:700;color:var(--color-primary)}.stat-label{font-size:12px;color:var(--color-text-muted)}.stat-details{color:var(--color-text-muted);font-size:15px}.settings-section{background:var(--color-surface);border-radius:var(--radius);padding:20px;margin-bottom:16px}.settings-section h2{font-size:16px;margin-bottom:12px;color:var(--color-text-muted)}.settings-section p{font-size:14px;line-height:1.6;color:var(--color-text-muted);margin-bottom:8px}.confirm-reset{display:flex;flex-direction:column;gap:12px}.confirm-buttons{display:flex;gap:10px}@media(max-width:400px){.mc-options{grid-template-columns:1fr}.rating-row{grid-template-columns:repeat(2,1fr)}.summary-cards{grid-template-columns:1fr}}