:root{--purple:#6d3ce6;--dark:#211735;--bg:#f5f2fb;--card:#fff;--text:#211c2c;--muted:#777184;--border:#e6e0ef;--danger:#c63f52}
*{box-sizing:border-box}body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;color:var(--text);background:var(--bg)}
a{color:var(--purple);text-decoration:none}.layout{display:grid;grid-template-columns:220px 1fr;min-height:100vh}.sidebar{background:var(--dark);color:#fff;padding:28px 16px;position:sticky;top:0;height:100vh}.brand{font-size:20px;font-weight:700;line-height:1.35;margin-bottom:28px}.brand strong{color:#bba6ff}.sidebar nav{display:grid;gap:8px}.sidebar nav a,.linkbtn{color:#eee;background:transparent;border:0;text-align:left;width:100%;padding:12px;border-radius:10px;font-size:15px}.sidebar nav a:hover,.sidebar nav a.active,.linkbtn:hover{background:#392852}.logout{position:absolute;left:16px;right:16px;bottom:20px}.main{padding:30px;min-width:0}.page-head,.section-head{display:flex;justify-content:space-between;align-items:center;gap:16px;margin-bottom:20px}.page-head h1{margin:0;color:var(--purple);font-size:30px}.page-head p{margin:7px 0 0;color:var(--muted)}.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:14px;margin-bottom:18px}.stat,.card{background:var(--card);border-radius:18px;box-shadow:0 8px 30px rgba(56,35,93,.06)}.stat{padding:22px}.stat span{display:block;color:var(--muted)}.stat strong{font-size:32px;color:var(--purple)}.card{padding:22px;margin-bottom:18px}.card h2{margin-top:0}.grid.cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:14px}.class-card{display:block;border:1px solid var(--border);border-radius:14px;padding:16px;color:var(--text)}.class-card div:first-child{display:flex;flex-direction:column;gap:5px}.class-card span,.class-card small{color:var(--muted)}.code{margin:14px 0;font-size:22px;font-weight:800;color:var(--purple);letter-spacing:2px}.two-col{display:grid;grid-template-columns:1fr 1.4fr;gap:18px}.narrow{max-width:820px}.form-grid{display:grid;grid-template-columns:1fr 1fr;gap:14px}.form-grid .full{grid-column:1/-1}label{display:grid;gap:7px;font-size:14px;color:#5f586b}input,textarea,select{width:100%;border:1px solid var(--border);border-radius:10px;padding:11px 12px;font:inherit;background:#fff}input:focus,textarea:focus,select:focus{outline:2px solid #d9ccff;border-color:var(--purple)}.btn{display:inline-flex;align-items:center;justify-content:center;border:1px solid var(--border);background:#fff;color:var(--text);border-radius:10px;padding:10px 15px;font-weight:600;cursor:pointer}.btn.primary{background:var(--purple);border-color:var(--purple);color:#fff}.btn.danger{background:#fff0f2;border-color:#f4c8cf;color:var(--danger)}.wide{width:100%}.actions,.danger-zone,.toolbar,.inline-form{display:flex;align-items:center;gap:10px;flex-wrap:wrap}.danger-zone{border-top:1px solid var(--border);margin-top:20px;padding-top:16px}.toolbar{margin-bottom:14px}.toolbar>input{flex:1;min-width:220px}.toolbar select{width:auto}.check{display:flex;grid-template:none;align-items:center;gap:7px}.check input{width:auto}.table-wrap{overflow:auto}table{width:100%;border-collapse:collapse}th,td{text-align:left;padding:13px 10px;border-bottom:1px solid var(--border);white-space:nowrap}th{color:var(--muted);font-size:13px}.pill{display:inline-block;background:#efe9ff;color:var(--purple);border-radius:999px;padding:4px 9px;font-weight:700}.empty{text-align:center;color:var(--muted);padding:34px}.flash{padding:13px 16px;border-radius:12px;margin-bottom:16px;background:#ecf8f0;color:#237743}.flash.error{background:#fff0f2;color:var(--danger)}.hint,.muted{color:var(--muted)}hr{border:0;border-top:1px solid var(--border);margin:20px 0}.auth-bg{min-height:100vh;display:grid;place-items:center;background:linear-gradient(135deg,#f6f2ff,#ece6fa)}.auth-card{width:min(420px,calc(100% - 32px));background:#fff;padding:34px;border-radius:22px;box-shadow:0 20px 60px rgba(46,28,78,.13)}.auth-card h1{margin:0;color:var(--purple)}.auth-card form{display:grid;gap:14px;margin-top:24px}details summary{list-style:none}
@media(max-width:900px){.layout{grid-template-columns:1fr}.sidebar{position:static;height:auto}.sidebar nav{grid-template-columns:repeat(3,1fr)}.logout{position:static;margin-top:10px}.main{padding:18px}.stats{grid-template-columns:repeat(2,1fr)}.two-col{grid-template-columns:1fr}}
@media(max-width:600px){.form-grid{grid-template-columns:1fr}.stats{grid-template-columns:1fr 1fr}.page-head{align-items:flex-start}.sidebar nav{grid-template-columns:1fr}.main{padding:12px}.card{padding:16px;border-radius:14px}}

.list-row{display:flex;align-items:center;justify-content:space-between;gap:14px;padding:14px 4px;border-bottom:1px solid var(--border);color:var(--text)}
.list-row>div:first-child{display:grid;gap:5px}.list-row small{color:var(--muted)}.small-stat{font-size:22px!important}
.option-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:12px;padding:14px;background:#faf8ff;border-radius:12px}
.danger-card{border:1px solid #f4c8cf}.review-grid{display:grid;grid-template-columns:1.5fr .8fr;gap:18px}
.media-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(170px,1fr));gap:14px}.media-card{display:grid;gap:8px;border:1px solid var(--border);padding:10px;border-radius:14px;color:var(--text)}
.media-card img{width:100%;height:190px;object-fit:cover;border-radius:9px;background:#eee}.pdf-box{height:190px;display:grid;place-items:center;background:#efe9ff;color:var(--purple);font-size:32px;font-weight:800;border-radius:9px}
.student-bg{background:#f5f2fb;min-height:100vh}.student-head{height:68px;background:#211735;color:#fff;display:flex;align-items:center;justify-content:space-between;padding:0 max(16px,calc((100% - 900px)/2));gap:16px}.student-head a{color:#fff}.student-head div{display:grid}.student-head span{font-size:13px;color:#c8bdd9}
.student-main{max-width:900px;margin:auto;padding:22px 16px}.student-main h1{color:var(--purple)}.assignment-cards{display:grid;gap:14px}.student-assignment{display:flex;justify-content:space-between;align-items:center;background:#fff;border-radius:16px;padding:20px;color:var(--text);box-shadow:0 8px 30px rgba(56,35,93,.06)}
.student-assignment>div:first-child{display:grid;gap:6px}.student-assignment small{color:var(--muted)}.student-assignment.closed{opacity:.65}.submit-state{color:var(--purple);font-weight:700}.upload-box{border:2px dashed #cdbff4;border-radius:14px;padding:20px;background:#faf8ff}.upload-box span{color:var(--muted);font-size:13px}.upload-box input{border:0;padding:10px 0}em{color:var(--danger);font-style:normal;margin-left:5px}
@media(max-width:900px){.review-grid{grid-template-columns:1fr}.option-grid{grid-template-columns:1fr}}