:root{--navy:#102a43;--blue:#2563eb;--blue-dark:#1d4ed8;--blue-soft:#eff6ff;--green:#15803d;--green-soft:#f0fdf4;--amber:#b45309;--amber-soft:#fffbeb;--red:#b42318;--red-soft:#fff1f0;--text:#334155;--muted:#64748b;--line:#e2e8f0;--bg:#f8fafc;--card:#fff}
*{box-sizing:border-box}
body{margin:0;min-height:100vh;font-family:Inter,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:var(--text);background:var(--bg)}
button,input{font:inherit}button{cursor:pointer}
#loader{position:fixed;inset:0;z-index:10;display:grid;place-content:center;gap:1rem;text-align:center;color:var(--navy);font-weight:800;background:var(--bg);transition:opacity .25s ease,visibility .25s ease}
#loader.hidden{opacity:0;visibility:hidden}
.spinner{width:42px;height:42px;margin:auto;border:4px solid var(--blue-soft);border-top-color:var(--blue);border-radius:50%;animation:spin .8s linear infinite}
@keyframes spin{to{transform:rotate(360deg)}}
.app{min-height:100vh;display:grid;grid-template-columns:240px minmax(0,1fr)}
.side{display:flex;flex-direction:column;padding:24px 18px;background:var(--navy);color:#fff}
.brand{font-weight:800;font-size:20px;margin-bottom:28px}.brand small{display:block;font-size:12px;font-weight:500;opacity:.7;margin-top:4px}
.nav{display:grid;gap:8px}.nav button{display:flex;align-items:center;gap:10px;border:0;border-radius:12px;padding:12px 14px;text-align:left;background:transparent;color:#cbd5e1;font-weight:700}.nav button.active,.nav button:hover{background:rgba(255,255,255,.12);color:#fff}
.logout{margin-top:auto;border:1px solid rgba(255,255,255,.18);border-radius:12px;padding:11px 14px;background:transparent;color:#fff;font-weight:700}.logout:hover{background:rgba(255,255,255,.1)}
.main{padding:28px;max-width:1280px;width:100%;margin:auto}
.top{display:flex;justify-content:space-between;gap:16px;align-items:center;margin-bottom:22px}
.student{display:flex;gap:10px;align-items:center;font-weight:800;color:var(--navy)}.avatar{display:grid;place-items:center;width:42px;height:42px;border-radius:14px;background:var(--blue-soft);color:var(--blue-dark)}
.search{width:min(380px,100%);padding:11px 13px;border:1px solid var(--line);border-radius:12px;background:#fff;outline:none}.search:focus{border-color:var(--blue);box-shadow:0 0 0 3px rgba(37,99,235,.12)}
.view{display:none}.view.active{display:block}
.hero{display:grid;grid-template-columns:1.3fr .7fr;gap:22px;padding:28px;border-radius:24px;color:#fff;background:linear-gradient(135deg,var(--navy),var(--blue))}
.hero h1{margin:6px 0 12px;font-size:clamp(28px,5vw,48px);line-height:1.05}.hero p{margin:0;line-height:1.6;opacity:.92}
.focus{align-self:stretch;padding:18px;border:1px solid rgba(255,255,255,.25);border-radius:18px;background:rgba(255,255,255,.12)}.focus strong{display:block;font-size:34px;margin:8px 0}.track{height:9px;background:rgba(255,255,255,.25);border-radius:99px;overflow:hidden}.fill{height:100%;width:0;background:#fff;transition:width .25s ease}
.next{display:flex;gap:10px;align-items:center;margin-top:16px;flex-wrap:wrap}.next small{color:#dbeafe}
.metrics{display:grid;grid-template-columns:repeat(4,1fr);gap:14px;margin:18px 0}.metric,.card{background:var(--card);border:1px solid var(--line);border-radius:18px}.metric{padding:18px}.metric span{font-size:12px;color:var(--muted);font-weight:800;text-transform:uppercase}.metric strong{display:block;color:var(--navy);font-size:28px;margin-top:7px}.metric small{display:block;color:var(--muted);margin-top:5px;line-height:1.4}
.grid{display:grid;grid-template-columns:1.15fr .85fr;gap:18px}.dashboard-material{margin-top:18px}.card{padding:20px}.card h2{margin:0 0 14px;color:var(--navy);font-size:18px}.card-intro{margin:-4px 0 16px;color:var(--muted);font-size:14px;line-height:1.55}
.list{display:grid;gap:10px}.item{display:flex;gap:12px;justify-content:space-between;align-items:center;padding:14px;border:1px solid var(--line);border-radius:14px;background:#fff}.item-main{min-width:0;flex:1}.item h3,.item-title{margin:0;color:var(--navy);font-size:15px;font-weight:800;line-height:1.4}.item p,.item-meta{margin:4px 0 0;color:var(--muted);font-size:13px;line-height:1.5}
.badge{flex:none;padding:6px 9px;border-radius:999px;background:var(--blue-soft);color:var(--blue-dark);font-size:11px;font-weight:800;white-space:nowrap}.badge.good{background:var(--green-soft);color:var(--green)}
.primary,.download,.secondary{display:inline-flex;align-items:center;justify-content:center;text-decoration:none;border-radius:12px;padding:11px 14px;font-weight:800}.primary,.download{border:0;background:var(--blue);color:#fff}.primary:hover,.download:hover{background:var(--blue-dark)}.secondary{border:1px solid var(--line);background:#fff;color:var(--navy)}.secondary:hover{border-color:#bfdbfe;background:var(--blue-soft)}
.actions{display:flex;gap:9px;flex-wrap:wrap;margin-top:14px}
.task{cursor:pointer}.task.done{opacity:.65}.task.done h3{text-decoration:line-through}.check{flex:none;width:24px;height:24px;border:2px solid #94a3b8;border-radius:8px;display:grid;place-items:center;color:transparent}.task.done .check{border-color:var(--green);background:var(--green);color:#fff}
.lesson-summary{display:grid;grid-template-columns:130px 1fr auto;gap:18px;align-items:center;padding:18px;border:1px solid var(--line);border-radius:16px;background:#fff}.lesson-date{color:var(--muted);font-size:13px;font-weight:700}.lesson-title{margin:3px 0;color:var(--navy);font-weight:800}.lesson-score{text-align:center;min-width:86px;padding:12px;border-radius:14px;background:var(--green-soft);color:var(--green)}.lesson-score strong{display:block;font-size:24px}.lesson-score small{font-weight:700}
.lesson-detail{margin-top:10px;padding:18px;border:1px solid var(--line);border-radius:16px;background:#fff}.lesson-detail summary{cursor:pointer;color:var(--blue-dark);font-weight:800}.lesson-body{display:grid;grid-template-columns:1fr 1fr;gap:18px;margin-top:18px}.lesson-body h3{margin:0 0 8px;color:var(--navy);font-size:15px}.lesson-body ul{margin:0;padding-left:20px;color:var(--muted);line-height:1.7}.note{padding:14px;border-radius:14px;background:var(--amber-soft);color:#78350f;line-height:1.55}
.formula{margin-top:14px;padding:14px;border-radius:14px;background:var(--blue-soft);color:var(--navy);font-size:13px;line-height:1.55}
.empty{padding:18px;color:var(--muted);text-align:center;border:1px dashed var(--line);border-radius:14px}
.error{max-width:540px;margin:10vh auto;padding:2rem;border-radius:22px;text-align:center;background:#fff;box-shadow:0 18px 50px rgba(15,23,42,.12)}.error h1{color:var(--navy);font-size:1.7rem}.error a{display:inline-block;margin-top:1.2rem;padding:.8rem 1rem;border-radius:12px;color:#fff;background:var(--blue);text-decoration:none;font-weight:800}
@media(max-width:900px){.app{grid-template-columns:1fr}.side{padding:12px;position:sticky;top:0;z-index:3;display:flex;flex-direction:row;align-items:center;gap:10px;overflow:auto}.brand{display:none}.nav{display:flex}.nav button{white-space:nowrap}.logout{margin:0;white-space:nowrap}.main{padding:18px}.hero,.grid,.lesson-body{grid-template-columns:1fr}.metrics{grid-template-columns:repeat(2,1fr)}.lesson-summary{grid-template-columns:1fr auto}.lesson-date{grid-column:1/-1}}
@media(max-width:560px){.top{align-items:flex-start;flex-direction:column}.metrics{grid-template-columns:1fr}.hero{padding:20px}.item{align-items:flex-start}.lesson-summary{grid-template-columns:1fr}.lesson-score{text-align:left}.actions a,.actions button{width:100%}}