:root{--bg:#f7f9ff;--card:#fff;--border:#d9e3f5;--text:#22324d;--muted:#5f7391;--primary:#5b6cff;--primary-dark:#4454d8;--soft:#eef2ff;--ok:#159a6b;--err:#c63b3b}
*{box-sizing:border-box}
body{margin:0;font-family:Inter,Arial,sans-serif;background:var(--bg);color:var(--text)}
.container{max-width:1100px;margin:0 auto;padding:20px}
.topbar{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap}
.brand{font-weight:800;background:#fff;border:1px solid var(--border);padding:8px 12px;border-radius:999px;color:#4357a8}
.card{background:var(--card);border:1px solid var(--border);border-radius:14px;padding:16px}
.grid-2{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}
.grid-3{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}
.grid-4{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:12px}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
label{display:block;font-weight:700;color:var(--muted);margin:8px 0 6px}
input,select,textarea{width:100%;padding:10px 12px;border:1px solid var(--border);border-radius:10px;background:#fff}
textarea{min-height:88px;resize:vertical}
button,.btn{display:inline-flex;align-items:center;justify-content:center;padding:10px 14px;border-radius:10px;border:none;background:var(--primary);color:#fff;text-decoration:none;cursor:pointer}
button:hover,.btn:hover{background:var(--primary-dark)}
.btn.secondary,button.secondary{background:var(--soft);color:#304ea0;border:1px solid #d3defc}
.muted{color:var(--muted)}
.ok{color:var(--ok)}
.err{background:#fff1f1;border:1px solid #f3c4c4;color:var(--err);padding:10px;border-radius:10px}
.tag{display:inline-block;padding:3px 8px;border-radius:999px;background:#e5f8f0;color:#1f5f52;font-size:.8rem}
#exchange{min-height:220px;max-height:340px;overflow:auto;background:#fbfcff;border:1px solid var(--border);border-radius:10px;padding:10px}
.teacher-box{min-height:120px;max-height:120px;overflow:auto;background:#fbfcff;border:1px solid var(--border);border-radius:10px;padding:10px}
.notebook-sheet{background:repeating-linear-gradient(to bottom,#fff 0,#fff 30px,#d8e7ff 31px,#fff 32px);border:1px solid #c9dbfa;border-radius:14px;padding:14px 16px;position:relative;overflow:hidden}
.notebook-sheet:before{content:"";position:absolute;left:40px;top:0;bottom:0;width:2px;background:#ffb7b7}
.handwritten{font-family:"Comic Sans MS","Segoe Print",cursive;font-size:1.08rem}
.word-chip{display:inline-block;background:#fff;border:1px dashed #9cb8e6;border-radius:10px;padding:6px 10px;margin:4px;cursor:pointer}
.word-chip:hover{background:#eef5ff}
.note-detail{margin-top:10px;padding:10px;border:1px solid #cfe0ff;border-radius:10px;background:#f9fcff}
.folder-tabs{display:flex;gap:8px;align-items:flex-end;flex-wrap:wrap;margin:8px 0 0;padding-left:6px}
.folder-tab{display:inline-block;padding:10px 16px;text-decoration:none;border:2px solid #c7b6f7;border-bottom:none;border-radius:14px 14px 0 0;background:#ece5ff;color:#4d3a9f;font-weight:800;position:relative;top:2px}
.folder-tab.active{background:#7b63f3;color:#fff;top:4px;z-index:2}
.folder-body{margin-top:0 !important;border-top-left-radius:0;border-top-right-radius:14px}
.home-cards{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px}
@media (max-width:980px){.grid-4,.grid-3,.grid-2,.home-cards{grid-template-columns:1fr}.notebook-sheet:before{left:24px}}