:root{
  --bg:#f4f6fb; --card:#fff; --ink:#20242e; --muted:#7a8194;
  --accent:#4c6ef5; --accent-2:#7048e8; --danger:#e03131; --ok:#2f9e44;
}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,"Segoe UI",Roboto,Arial,sans-serif;background:var(--bg);color:var(--ink)}
.topbar{background:linear-gradient(90deg,var(--accent),var(--accent-2));color:#fff;padding:14px 20px;display:flex;align-items:center}
.topbar.student{background:linear-gradient(90deg,#12b886,#0ca678)}
.logo{color:#fff;font-weight:700;text-decoration:none;font-size:18px}
.crumb{color:#e7ecff}
.container{max-width:860px;margin:24px auto;padding:0 16px}
.card{background:var(--card);border-radius:14px;padding:18px 20px;margin-bottom:18px;box-shadow:0 1px 4px rgba(20,30,60,.08)}
h2{margin:0 0 12px;font-size:18px}
h3{margin:0 0 10px;font-size:16px}
.row{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.col{display:flex;flex-direction:column;gap:8px;margin-top:8px}
input[type=text]{padding:9px 12px;border:1px solid #d3d8e4;border-radius:8px;font-size:14px;min-width:160px;flex:1}
input[type=file]{font-size:13px}
label{font-size:13px;color:var(--muted);display:flex;flex-direction:column;gap:4px}
.btn{display:inline-block;padding:9px 14px;border-radius:8px;border:1px solid #d3d8e4;background:#fff;color:var(--ink);
     font-size:14px;cursor:pointer;text-decoration:none;transition:.15s}
.btn:hover{border-color:var(--accent);color:var(--accent)}
.btn.primary{background:var(--accent);border-color:var(--accent);color:#fff}
.btn.primary:hover{background:var(--accent-2);border-color:var(--accent-2);color:#fff}
.btn.danger{background:#fff;border-color:#f3c1c1;color:var(--danger)}
.btn.danger:hover{background:var(--danger);color:#fff;border-color:var(--danger)}
.btn.small{padding:6px 10px;font-size:13px}
.btn.tiny{padding:3px 8px;font-size:12px}
.hint{color:var(--muted);font-size:13px}
.hint.big{font-size:16px;text-align:center;padding:40px 0}
.error{color:var(--danger);font-size:14px}
table{width:100%;border-collapse:collapse}
td{padding:10px 4px;border-bottom:1px solid #eef0f5;vertical-align:middle}
tr:last-child td{border-bottom:none}
.right{text-align:right}
.share-row{display:flex;gap:8px;flex-wrap:wrap}
.share-row input{font-family:monospace}

/* дерево категорий */
ul.tree,ul.children{list-style:none;margin:0;padding:0}
ul.children{margin-left:18px;border-left:2px solid #e3e7f1;padding-left:12px}
.cat details{margin:6px 0}
.cat summary{cursor:pointer;padding:8px 10px;border-radius:8px;background:#eef1f8;list-style:none;display:flex;gap:10px;align-items:center;flex-wrap:wrap}
.cat summary::-webkit-details-marker{display:none}
.cat summary:hover{background:#e4e9f6}
.count{font-size:12px;color:var(--muted);background:#fff;border-radius:10px;padding:2px 8px}
.words{margin:8px 0 4px 10px}
.word-row{display:flex;align-items:center;gap:10px;padding:6px 0;border-bottom:1px dashed #e7eaf2}
.thumb{width:44px;height:44px;object-fit:cover;border-radius:8px;background:#e9edf5}
.thumb.placeholder{display:flex;align-items:center;justify-content:center;font-size:20px}
.word-info{flex:1;font-size:14px}
.w-front{font-weight:600}
.w-back{color:var(--accent-2);font-weight:600}
.dim{color:var(--muted);font-weight:400}
.add-word,.add-sub{margin:6px 0 6px 10px}
.add-word summary,.add-sub summary{cursor:pointer;color:var(--accent);font-size:13px}

/* карточки ученика (флип) */
.cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:12px;margin:12px 4px}
.flashcard{position:relative;aspect-ratio:1/1;cursor:pointer;perspective:800px}
.face{position:absolute;inset:0;border-radius:14px;background:#fff;box-shadow:0 2px 8px rgba(20,30,60,.12);
      display:flex;flex-direction:column;align-items:center;justify-content:center;gap:6px;padding:8px;
      backface-visibility:hidden;transition:transform .45s;overflow:hidden}
.face img{max-width:100%;max-height:70%;object-fit:contain}
.label{font-size:15px;font-weight:600}
.tap-hint{position:absolute;bottom:6px;right:8px;font-size:11px;color:var(--muted)}
.back{transform:rotateY(180deg);background:linear-gradient(135deg,var(--accent),var(--accent-2));color:#fff}
.hidden-word{font-size:20px;font-weight:800;text-align:center;word-break:break-word}
.flashcard.flipped .front{transform:rotateY(-180deg)}
.flashcard.flipped .back{transform:rotateY(0)}
.tree.student > .cat > details > summary{background:#dff9f0;font-size:16px}
.tree.student ul.children .cat > details > summary{background:#eef7f2}

/* отметки ученика в админке */
.mark-chip{font-size:12px;font-weight:600;border-radius:10px;padding:3px 10px;white-space:nowrap}
.mark-chip.know{background:#d9f7e8;color:#1c7c4c}
.mark-chip.unknown{background:#ffe3e3;color:#c22f4e}
.mark-chip.none{background:#eceff5;color:#8a93a6}
.t-progress{height:10px;border-radius:8px;background:#e9edf5;overflow:hidden;margin:8px 0 12px}
.t-progress-fill{height:100%;border-radius:8px;background:linear-gradient(90deg,var(--accent),var(--accent-2));transition:width .3s}