:root { --bg:#0f0f0f; --surface:#1a1a1a; --surface2:#242424; --surface3:#2e2e2e; --border:#333; --text:#e8e4de; --text2:#9a9590; --accent:#e07a5f; --accent2:#81b29a; --accent3:#f2cc8f; --danger:#e06070; --radius:12px; --shadow:0 4px 24px rgba(0,0,0,0.4); }
* { margin:0; padding:0; box-sizing:border-box; }
body { font-family:'DM Sans',sans-serif; background:var(--bg); color:var(--text); min-height:100vh; overflow-x:hidden; }
header { display:flex; align-items:center; justify-content:space-between; padding:14px 24px; border-bottom:1px solid var(--border); background:var(--surface); position:sticky; top:0; z-index:100; }
.logo { font-family:'DM Serif Display',serif; font-size:1.5rem; color:var(--accent); cursor:pointer; }
.logo span { color:var(--text2); font-size:0.85rem; margin-left:8px; font-family:'DM Sans'; }
.header-right { display:flex; align-items:center; gap:8px; }
.user-badge { display:inline-flex; align-items:center; gap:6px; padding:5px 14px 5px 8px; border-radius:20px; font-weight:600; font-size:0.85rem; cursor:pointer; transition:opacity 0.2s; border:none; font-family:'DM Sans'; }
.user-badge:hover { opacity:0.85; }
nav { display:flex; gap:4px; }
nav button { background:transparent; border:none; color:var(--text2); font-family:'DM Sans'; font-size:0.88rem; font-weight:500; padding:8px 14px; border-radius:8px; cursor:pointer; transition:all 0.2s; }
nav button:hover { background:var(--surface2); color:var(--text); }
nav button.active { background:var(--surface3); color:var(--accent); }
.container { max-width:900px; margin:0 auto; padding:28px 20px; }
.view { display:none; animation:fadeIn 0.3s ease; }
.view.active { display:block; }
@keyframes fadeIn { from{opacity:0;transform:translateY(10px)} to{opacity:1;transform:translateY(0)} }

/* Landing */
.landing { display:flex; flex-direction:column; align-items:center; justify-content:center; min-height:calc(100vh - 200px); padding:40px 20px; }
.landing h1 { font-family:'DM Serif Display',serif; font-size:2.2rem; margin-bottom:8px; text-align:center; }
.landing p { color:var(--text2); margin-bottom:40px; font-size:1.05rem; text-align:center; }
.user-grid { display:flex; gap:24px; flex-wrap:wrap; justify-content:center; }
.user-card { background:var(--surface); border:2px solid var(--border); border-radius:24px; padding:36px 48px; cursor:pointer; transition:all 0.3s; text-align:center; min-width:200px; }
.user-card:hover { transform:translateY(-6px); box-shadow:0 16px 48px rgba(0,0,0,0.5); }
.user-avatar-big { font-size:4rem; margin-bottom:12px; display:block; line-height:1; transition:transform 0.3s; }
.user-card:hover .user-avatar-big { transform:scale(1.15) rotate(-5deg); }
.user-card h3 { font-family:'DM Serif Display',serif; font-size:1.5rem; margin-bottom:6px; }
.user-card .meta { color:var(--text2); font-size:0.85rem; }
.user-card .change-avatar { font-size:0.78rem; color:var(--text2); margin-top:10px; opacity:0; transition:opacity 0.2s; text-decoration:underline; cursor:pointer; }
.user-card:hover .change-avatar { opacity:1; }
.parent-link { margin-top:32px; color:var(--text2); font-size:0.9rem; cursor:pointer; text-decoration:underline; transition:color 0.2s; }
.parent-link:hover { color:var(--accent); }

/* Avatar picker */
.avatar-grid { display:grid; grid-template-columns:repeat(6,1fr); gap:8px; margin-top:12px; }
.avatar-option { font-size:2rem; padding:10px; border-radius:12px; border:2px solid transparent; cursor:pointer; text-align:center; transition:all 0.2s; background:var(--surface2); }
.avatar-option:hover { transform:scale(1.15); border-color:var(--accent); }
.avatar-option.selected { border-color:var(--accent); background:var(--surface3); }

/* Deck grid */
.deck-grid { display:grid; grid-template-columns:repeat(auto-fill,minmax(250px,1fr)); gap:14px; margin-top:20px; }
.deck-card { background:var(--surface); border:1px solid var(--border); border-radius:var(--radius); padding:22px; cursor:pointer; transition:all 0.25s; }
.deck-card:hover { transform:translateY(-2px); box-shadow:var(--shadow); }
.deck-card > * { pointer-events:none; }
.deck-card .deck-actions { pointer-events:auto; }
.deck-card h3 { font-family:'DM Serif Display',serif; font-size:1.15rem; margin-bottom:6px; }
.deck-card .meta { color:var(--text2); font-size:0.83rem; }
.deck-card .deck-actions { display:flex; gap:6px; margin-top:14px; }
.add-deck-card { background:transparent; border:2px dashed var(--border); border-radius:var(--radius); padding:22px; cursor:pointer; display:flex; align-items:center; justify-content:center; color:var(--text2); font-size:0.95rem; font-family:'DM Sans'; transition:all 0.25s; min-height:130px; }
.add-deck-card:hover { border-color:var(--accent); color:var(--accent); }
.folder-card { border-color:var(--accent3); background:var(--surface2); }
.folder-card:hover { border-color:var(--accent3); box-shadow:0 4px 16px var(--accent3)33; }
.deck-card.drag-over { border-color:var(--accent); background:var(--accent)11; transform:scale(1.02); }
.drop-to-root { cursor:default; }
.breadcrumb { display:flex; align-items:center; gap:6px; font-size:0.9rem; flex-wrap:wrap; }
.breadcrumb-link { color:var(--accent); cursor:pointer; text-decoration:underline; }
.breadcrumb-link:hover { opacity:0.8; }
.breadcrumb-sep { color:var(--text2); }
.breadcrumb-current { color:var(--text); font-weight:600; }

/* Buttons */
.btn { display:inline-flex; align-items:center; gap:6px; padding:8px 16px; border-radius:8px; font-family:'DM Sans'; font-size:0.85rem; font-weight:600; border:none; cursor:pointer; transition:all 0.2s; }
.btn-primary { background:var(--accent); color:#fff; } .btn-primary:hover { background:#c96a50; }
.btn-secondary { background:var(--surface2); color:var(--text); border:1px solid var(--border); } .btn-secondary:hover { background:var(--surface3); }
.btn-success { background:var(--accent2); color:#0f0f0f; } .btn-success:hover { opacity:0.85; }
.btn-danger { background:transparent; color:var(--danger); border:1px solid var(--danger); } .btn-danger:hover { background:var(--danger); color:#fff; }
.btn-sm { padding:5px 10px; font-size:0.78rem; } .btn-lg { padding:12px 28px; font-size:1rem; }

/* Modal */
.modal-overlay { position:fixed; inset:0; background:rgba(0,0,0,0.7); display:flex; align-items:center; justify-content:center; z-index:200; animation:fadeIn 0.2s ease; padding:20px; }
.modal { background:var(--surface); border:1px solid var(--border); border-radius:16px; padding:28px; width:100%; max-width:560px; max-height:90vh; overflow-y:auto; }
.modal h2 { font-family:'DM Serif Display',serif; font-size:1.3rem; margin-bottom:18px; }
.form-group { margin-bottom:14px; }
.form-group label { display:block; font-size:0.8rem; font-weight:600; color:var(--text2); margin-bottom:5px; text-transform:uppercase; letter-spacing:0.5px; }
.form-group input,.form-group textarea { width:100%; padding:10px 14px; background:var(--surface2); border:1px solid var(--border); border-radius:8px; color:var(--text); font-family:'DM Sans'; font-size:0.93rem; outline:none; }
.form-group textarea { min-height:90px; resize:vertical; font-family:'JetBrains Mono',monospace; font-size:0.85rem; line-height:1.6; }
.form-group input:focus,.form-group textarea:focus { border-color:var(--accent); }
.form-actions { display:flex; gap:8px; justify-content:flex-end; margin-top:18px; flex-wrap:wrap; }
.hint { font-size:0.76rem; color:var(--text2); margin-top:4px; font-style:italic; }
.math-preview { background:var(--surface2); border:1px solid var(--border); border-radius:8px; padding:12px 14px; margin-top:6px; min-height:36px; font-size:1.05rem; overflow-x:auto; }

/* Card table */
.card-list-header { display:flex; align-items:center; justify-content:space-between; margin-bottom:18px; flex-wrap:wrap; gap:10px; }
.card-list-header h2 { font-family:'DM Serif Display',serif; font-size:1.4rem; }
.card-table { width:100%; border-collapse:collapse; }
.card-table th { text-align:left; font-size:0.76rem; text-transform:uppercase; letter-spacing:0.5px; color:var(--text2); padding:8px 10px; border-bottom:1px solid var(--border); }
.card-table td { padding:10px; border-bottom:1px solid var(--border); font-size:0.88rem; vertical-align:top; }
.card-table tr:hover { background:var(--surface2); }
.card-content { max-width:280px; overflow:hidden; text-overflow:ellipsis; white-space:nowrap; }
.sr-badge { display:inline-block; padding:2px 8px; border-radius:4px; font-size:0.73rem; font-weight:600; }
.sr-new { background:#2a3f35; color:var(--accent2); } .sr-learning { background:#3f3520; color:var(--accent3); } .sr-review { background:#2a2a2a; color:var(--text2); }

/* Study */
.study-container { display:flex; flex-direction:column; align-items:center; padding-top:20px; }
.study-progress { width:100%; max-width:600px; display:flex; align-items:center; gap:12px; margin-bottom:8px; color:var(--text2); font-size:0.85rem; }
.progress-bar { flex:1; height:4px; background:var(--surface3); border-radius:2px; overflow:hidden; }
.progress-fill { height:100%; border-radius:2px; transition:width 0.4s ease; }
.streak-bar { width:100%; max-width:600px; display:flex; align-items:center; justify-content:center; gap:8px; margin-bottom:24px; padding:8px 16px; border-radius:10px; background:var(--surface); border:1px solid var(--border); font-size:0.9rem; transition:all 0.3s; }
.streak-bar.hot { border-color:#e07a5f; background:#2a1a15; } .streak-bar.fire { border-color:#f0a030; background:#2a2010; animation:pulse 0.6s ease; }
@keyframes pulse { 0%,100%{transform:scale(1)} 50%{transform:scale(1.03)} }
.flashcard { width:100%; max-width:600px; min-height:300px; perspective:1000px; cursor:pointer; margin-bottom:28px; }
.flashcard-inner { position:relative; width:100%; min-height:300px; transition:transform 0.5s cubic-bezier(0.4,0,0.2,1); transform-style:preserve-3d; }
.flashcard.flipped .flashcard-inner { transform:rotateY(180deg); }
.flashcard-front,.flashcard-back { position:absolute; inset:0; backface-visibility:hidden; background:var(--surface); border:1px solid var(--border); border-radius:16px; padding:36px 28px; display:flex; flex-direction:column; align-items:center; justify-content:center; text-align:center; font-size:1.15rem; line-height:1.6; overflow-y:auto; }
.flashcard-front { z-index:2; } .flashcard-back { transform:rotateY(180deg); background:var(--surface2); }
.flashcard-label { position:absolute; top:14px; left:18px; font-size:0.68rem; text-transform:uppercase; letter-spacing:1px; color:var(--text2); font-weight:600; }
.flashcard .katex { font-size:1.3rem; }
.study-actions { display:flex; gap:10px; flex-wrap:wrap; justify-content:center; }
.study-actions .btn { min-width:100px; justify-content:center; }
.rating-again { background:var(--danger); color:#fff; } .rating-hard { background:#b08040; color:#fff; } .rating-good { background:var(--accent2); color:#0f0f0f; } .rating-easy { background:#5090d0; color:#fff; }
.study-done { text-align:center; padding:50px 20px; }
.study-done h2 { font-family:'DM Serif Display',serif; font-size:1.8rem; margin-bottom:10px; color:var(--accent2); }

/* Stats */
.stats-grid { display:grid; grid-template-columns:repeat(auto-fit,minmax(120px,1fr)); gap:12px; margin:20px 0; }
.stat-card { background:var(--surface); border:1px solid var(--border); border-radius:var(--radius); padding:16px; text-align:center; }
.stat-card .value { font-family:'DM Serif Display',serif; font-size:1.6rem; }
.stat-card .label { font-size:0.73rem; color:var(--text2); margin-top:4px; text-transform:uppercase; letter-spacing:0.5px; }
.chart-bar-container { display:flex; align-items:flex-end; gap:4px; height:100px; margin:16px 0; padding:0 4px; }
.chart-bar-wrap { flex:1; display:flex; flex-direction:column; align-items:center; gap:4px; }
.chart-bar { width:100%; border-radius:4px 4px 0 0; min-height:2px; transition:height 0.4s ease; }
.chart-bar-label { font-size:0.6rem; color:var(--text2); }
.deck-stat-row { display:flex; align-items:center; justify-content:space-between; padding:10px 14px; background:var(--surface); border:1px solid var(--border); border-radius:8px; margin-bottom:6px; font-size:0.85rem; }
.deck-stat-name { font-weight:600; }
.deck-stat-nums { display:flex; gap:16px; color:var(--text2); font-size:0.8rem; }
.section-title { font-family:'DM Serif Display',serif; font-size:1.1rem; margin:24px 0 10px; }
.import-export { display:flex; gap:8px; margin-top:10px; flex-wrap:wrap; }

/* Parent dashboard */
.parent-header { display:flex; align-items:center; justify-content:space-between; margin-bottom:20px; flex-wrap:wrap; gap:10px; }
.parent-header h2 { font-family:'DM Serif Display',serif; font-size:1.5rem; }
.parent-user-summary { background:var(--surface); border:1px solid var(--border); border-radius:var(--radius); padding:20px; margin-bottom:16px; }
.parent-user-header { display:flex; align-items:center; gap:12px; margin-bottom:14px; }
.parent-user-header .pu-avatar { font-size:2rem; }
.parent-user-header .pu-name { font-family:'DM Serif Display',serif; font-size:1.2rem; }
.parent-mini-stats { display:grid; grid-template-columns:repeat(auto-fit,minmax(100px,1fr)); gap:8px; margin-bottom:12px; }
.parent-mini-stat { text-align:center; padding:8px; background:var(--surface2); border-radius:8px; }
.parent-mini-stat .pms-val { font-family:'DM Serif Display',serif; font-size:1.3rem; }
.parent-mini-stat .pms-lab { font-size:0.68rem; color:var(--text2); text-transform:uppercase; }
.week-dots { display:flex; gap:4px; align-items:flex-end; height:40px; }
.week-dot { flex:1; border-radius:3px 3px 0 0; min-height:3px; transition:height 0.3s; }
.week-dot-label { font-size:0.58rem; color:var(--text2); text-align:center; }
.session-table { width:100%; border-collapse:collapse; font-size:0.82rem; }
.session-table th { text-align:left; font-size:0.7rem; text-transform:uppercase; color:var(--text2); padding:6px 8px; border-bottom:1px solid var(--border); }
.session-table td { padding:8px; border-bottom:1px solid var(--border); }
.session-table tr:hover { background:var(--surface2); }
.accuracy-bar { display:inline-block; width:50px; height:6px; background:var(--surface3); border-radius:3px; overflow:hidden; vertical-align:middle; margin-left:4px; }
.accuracy-fill { height:100%; border-radius:3px; }

/* Reward */
.reward-msg { position:fixed; top:50%; left:50%; transform:translate(-50%,-50%); z-index:500; font-family:'DM Serif Display',serif; font-size:2.5rem; color:#fff; text-shadow:0 4px 20px rgba(0,0,0,0.6); pointer-events:none; animation:rewardPop 1.5s ease forwards; white-space:nowrap; }
@keyframes rewardPop { 0%{opacity:0;transform:translate(-50%,-50%) scale(0.5)} 20%{opacity:1;transform:translate(-50%,-50%) scale(1.1)} 40%{transform:translate(-50%,-50%) scale(1)} 80%{opacity:1} 100%{opacity:0;transform:translate(-50%,-60%) scale(1)} }
#particles-canvas { position:fixed; inset:0; z-index:400; pointer-events:none; }

.empty-state { text-align:center; padding:50px 20px; color:var(--text2); }
.empty-state h3 { font-family:'DM Serif Display',serif; font-size:1.2rem; color:var(--text); margin-bottom:8px; }
.type-input-wrap { width:100%; max-width:600px; margin-bottom:20px; }
.type-input { width:100%; padding:14px 18px; background:var(--surface); border:2px solid var(--border); border-radius:12px; color:var(--text); font-family:'DM Sans'; font-size:1.1rem; text-align:center; outline:none; transition:border-color 0.3s; }
.type-input:focus { border-color:var(--accent); }
.type-input.correct { border-color:var(--accent2); background:#1a2f25; }
.type-input.wrong { border-color:var(--danger); background:#2f1a1a; }
.type-result { width:100%; max-width:600px; padding:16px; border-radius:12px; margin-bottom:16px; text-align:center; font-size:1rem; }
.type-result.correct { background:#1a2f25; border:1px solid var(--accent2); color:var(--accent2); }
.type-result.wrong { background:#2f1a1a; border:1px solid var(--danger); color:var(--danger); }
.type-result .expected { margin-top:8px; font-size:0.9rem; color:var(--text); }
.mode-badge { display:inline-block; padding:2px 8px; border-radius:4px; font-size:0.7rem; font-weight:600; text-transform:uppercase; margin-left:8px; }
.mode-self { background:#2a2a2a; color:var(--text2); }
.mode-type { background:#2a3520; color:var(--accent2); }
.toast { position:fixed; bottom:20px; right:20px; background:var(--surface2); border:1px solid var(--border); color:var(--text); padding:10px 18px; border-radius:10px; font-size:0.88rem; z-index:300; animation:slideUp 0.3s ease,fadeOut 0.3s ease 2.5s forwards; box-shadow:var(--shadow); }
@keyframes slideUp { from{transform:translateY(20px);opacity:0} to{transform:translateY(0);opacity:1} }
@keyframes fadeOut { to{opacity:0;transform:translateY(10px)} }
/* Markdown content inside flashcards */
.flashcard-front table, .flashcard-back table, .math-preview table, .type-result table {
  border-collapse:collapse; margin:8px 0; width:auto;
}
.flashcard-front th, .flashcard-back th, .math-preview th, .type-result th {
  background:var(--surface3); font-size:0.85rem; font-weight:600; text-align:left; padding:8px 14px; border:1px solid var(--border);
}
.flashcard-front td, .flashcard-back td, .math-preview td, .type-result td {
  padding:6px 14px; border:1px solid var(--border); font-size:0.9rem;
}
.flashcard-front tr:hover, .flashcard-back tr:hover { background:var(--surface3); }
.flashcard-front p, .flashcard-back p, .type-result .expected p { margin:0.4em 0; }
.flashcard-front code, .flashcard-back code { background:var(--surface3); padding:1px 5px; border-radius:4px; font-family:'JetBrains Mono',monospace; font-size:0.88em; }
.katex-display { margin:0.5em 0; }

@media (max-width:600px) {
  header { padding:12px 14px; flex-wrap:wrap; gap:6px; }
  .container { padding:16px 14px; }
  .flashcard-front,.flashcard-back { padding:28px 18px; font-size:1rem; }
  nav button { padding:6px 10px; font-size:0.8rem; }
  .card-table th:nth-child(2),.card-table td:nth-child(2) { display:none; }
  .landing h1 { font-size:1.7rem; }
  .user-card { padding:28px 32px; min-width:160px; }
  .avatar-grid { grid-template-columns:repeat(5,1fr); }
  .reward-msg { font-size:1.8rem; }
}