:root{
  --bg:#0b1220;
  --panel:#0f172a;
  --panel2:#07111f;
  --card:#020617;
  --card2:#0b1220;
  --ring:#1f2937;
  --ring2:#334155;
  --ink:#e5e7eb;
  --muted:#9ca3af;
  --soft:#cbd5e1;
  --blue:#4f46e5;
  --blue2:#2563eb;
  --green:#16a34a;
  --red:#ef4444;
  --amber:#f59e0b;
  --shadow:0 24px 70px rgba(0,0,0,.38);
  --radius:16px;
}
*{box-sizing:border-box}
html{min-height:100%;background:var(--bg)}
body.page{
  min-height:100vh;
  margin:0;
  background:
    radial-gradient(circle at 20% 0%, rgba(79,70,229,.18), transparent 28rem),
    radial-gradient(circle at 100% 10%, rgba(37,99,235,.10), transparent 30rem),
    var(--bg);
  color:var(--ink);
  font:14px/1.5 system-ui,-apple-system,Segoe UI,Roboto,Ubuntu,Cantarell,Noto Sans,Helvetica,Arial;
}
a{color:inherit}
button,input,textarea,select{font:inherit}

/* Top navigation */
.top{
  position:sticky;
  top:0;
  z-index:20;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:14px;
  padding:10px 16px;
  border-bottom:1px solid var(--ring);
  background:linear-gradient(120deg,#07111f,#0b1a3a);
  box-shadow:0 10px 30px rgba(0,0,0,.24);
}
.brand,.brand-link{
  display:flex;
  align-items:center;
  gap:10px;
  min-width:0;
  color:#dbeafe;
  font-weight:800;
  text-decoration:none;
  letter-spacing:.2px;
}
.brand-link img,.brand img{width:96px;height:auto;display:block;flex:0 0 auto}
.brand-text{display:flex;flex-direction:column;min-width:0}
.brand-text strong{font-size:15px;line-height:1.1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.brand-text small{font-size:12px;color:var(--muted);font-weight:600;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.nav{display:flex;gap:8px;align-items:center;justify-content:flex-end;flex-wrap:wrap}
.nav a,.btn,button{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  gap:7px;
  min-height:40px;
  border:1px solid var(--ring);
  background:#111827;
  color:var(--ink);
  padding:8px 12px;
  border-radius:12px;
  text-decoration:none;
  cursor:pointer;
  user-select:none;
  transition:filter .15s ease, transform .15s ease, border-color .15s ease;
}
.nav a:hover,.btn:hover,button:hover{filter:brightness(1.08);border-color:var(--ring2)}
.nav a:active,.btn:active,button:active{transform:translateY(1px)}
.btn.primary,button{background:var(--blue);border-color:transparent;color:#fff}
.btn.blue{background:var(--blue2);border-color:transparent;color:#fff}
.btn.red{background:var(--red);border-color:transparent;color:#fff}
.btn.green{background:var(--green);border-color:transparent;color:#fff}
.btn.ghost{background:transparent;border-color:var(--ring);color:var(--soft)}
.btn.small{min-height:34px;padding:6px 10px;border-radius:10px;font-size:13px}
.btn.block,button.block{width:100%}

/* Layout */
.wrap{width:min(1120px,100%);margin:22px auto;padding:0 16px}
.auth-wrap{width:min(680px,100%);margin:22px auto;padding:0 16px}
.page-head{
  display:flex;
  align-items:flex-start;
  justify-content:space-between;
  gap:16px;
  margin:0 0 16px;
}
.page-head h1,.hero h1{margin:0;color:#f8fafc;font-size:clamp(28px,4.2vw,42px);letter-spacing:.06em;line-height:1.08}
.page-head p,.hero p{margin:7px 0 0;color:var(--soft);font-size:15px;max-width:760px}
.hero{
  display:grid;
  grid-template-columns:1.2fr .8fr;
  gap:14px;
  align-items:stretch;
  margin:0 0 16px;
}
.hero-card,.card{
  background:linear-gradient(180deg,rgba(15,23,42,.86),rgba(2,6,23,.96));
  border:1px solid var(--ring);
  border-radius:var(--radius);
  padding:18px;
  box-shadow:var(--shadow);
}
.card{margin-bottom:14px}
.card.narrow{max-width:650px;margin:0 auto 14px}
.card h1,.card h2,.card h3{margin:0 0 12px;color:#f8fafc;line-height:1.15}
.card h1{font-size:clamp(30px,4.4vw,40px);letter-spacing:.06em}
.card h2{font-size:20px}.card h3{font-size:16px}
.card .sub{margin-top:-4px;margin-bottom:14px;color:var(--soft)}
.muted{color:var(--muted)}
.soft{color:var(--soft)}

/* Cards and grids */
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));gap:14px}
.split{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:14px;align-items:start}
.stat-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:10px;margin-top:12px}
.stat{border:1px solid var(--ring);background:#0b1220;border-radius:14px;padding:12px}
.stat b{display:block;color:#dbeafe;font-size:24px;line-height:1.1}.stat span{display:block;color:var(--muted);font-size:12px;margin-top:4px}
.info-panel{border:1px solid var(--ring);background:#07111f;border-radius:14px;padding:14px;color:var(--soft)}

/* Forms */
.form{display:grid;gap:12px}
.form label{display:grid;gap:6px;color:var(--soft);font-size:15px}
input,textarea,select{
  width:100%;
  background:#0b1220;
  color:var(--ink);
  border:1px solid var(--ring);
  border-radius:12px;
  padding:12px 13px;
  min-height:48px;
  outline:none;
}
textarea{min-height:130px;resize:vertical;line-height:1.45}
input:focus,textarea:focus,select:focus{border-color:#60a5fa;box-shadow:0 0 0 3px rgba(96,165,250,.14)}
.form button{margin-top:2px;min-height:48px}
.action-row{display:grid;grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:10px;margin:14px 0 0}
.action-row .btn{width:100%;text-align:center}

/* Messages */
.ok,.err,.notice{
  padding:11px 12px;
  border-radius:12px;
  margin:10px 0 14px;
  line-height:1.45;
}
.ok{border:1px solid #14532d;background:#052e16;color:#dcfce7}
.err{border:1px solid #7f1d1d;background:#450a0a;color:#fee2e2}
.notice{border:1px solid #1e3a8a;background:#0b1a3a;color:#dbeafe}
code,.code{
  font:700 18px ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;
  color:#93c5fd;
}
.code-chip{
  display:inline-flex;
  align-items:center;
  border:1px solid #1d4ed8;
  background:#0b1a3a;
  color:#bfdbfe;
  border-radius:999px;
  padding:5px 10px;
  font:800 15px ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
}
.badge{
  display:inline-flex;
  align-items:center;
  justify-content:center;
  border:1px solid var(--ring);
  padding:4px 9px;
  border-radius:999px;
  background:#0b1220;
  color:#cbd5e1;
  font-size:12px;
  white-space:nowrap;
}
.badge.ok{border-color:#14532d;background:#052e16;color:#bbf7d0;margin:0}.badge.off{border-color:#7f1d1d;background:#450a0a;color:#fecaca;margin:0}

/* Tables */
.table-wrap{width:100%;overflow:auto;border:1px solid var(--ring);border-radius:14px;background:#020617}
table{width:100%;border-collapse:collapse;min-width:680px}
th,td{border-bottom:1px solid var(--ring);padding:11px 12px;text-align:left;vertical-align:top}
th{color:#cbd5e1;background:#07111f;font-size:12px;text-transform:uppercase;letter-spacing:.04em}
tr:last-child td{border-bottom:0}
td .muted{font-size:13px}.cell-actions{white-space:nowrap}.inline-form{display:inline}.inline-form button{min-height:34px;padding:6px 10px;border-radius:10px;background:#111827;border:1px solid var(--ring)}

/* Student assignment list */
.assignment-list{display:grid;gap:12px}
.assignment-item{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:12px;align-items:center;border:1px solid var(--ring);background:#0b1220;border-radius:14px;padding:14px}
.assignment-item h3{margin:0 0 6px}.assignment-item p{margin:0;color:var(--soft)}
.assignment-meta{display:flex;gap:8px;flex-wrap:wrap;margin-top:9px}

/* Auth pages */
.auth-card{padding:28px 24px}
.auth-logo{display:flex;align-items:center;gap:12px;margin-bottom:18px;color:#dbeafe;text-decoration:none;font-weight:800}.auth-logo img{width:106px;height:auto}
.auth-card h1{margin-bottom:10px}.auth-card .lead{color:var(--soft);font-size:16px;margin:0 0 18px}

/* Mobile */
@media(max-width:760px){
  .top{position:static;align-items:stretch;flex-direction:column;padding:10px 12px}
  .brand-link img,.brand img{width:88px}.nav{display:grid;grid-template-columns:1fr 1fr;gap:8px}.nav a{width:100%}
  .wrap,.auth-wrap{margin:16px auto;padding:0 12px}
  .hero{grid-template-columns:1fr}.split{grid-template-columns:1fr}.page-head{flex-direction:column}
  .card,.hero-card{padding:15px;border-radius:14px}.auth-card{padding:20px 16px}
  .action-row{grid-template-columns:1fr;gap:8px}
  table{min-width:620px}
  .assignment-item{grid-template-columns:1fr}.assignment-item .btn{width:100%}
}
@media(max-width:420px){
  .nav{grid-template-columns:1fr}.page-head h1,.hero h1,.card h1{letter-spacing:.03em}
}