/* EduDrone VPS – trang đăng nhập & giáo viên (dùng chung token màu với lõi) */
:root {
  --bg: #eef2f7; --card: #ffffff; --ink: #1d2433; --muted: #6b7686; --line: #d9e0ea; --soft: #f6f8fb;
  --hdr: #142033; --blue: #2e86de; --green: #10ac84; --red: #e74c3c; --amber: #f39c12;
  --okBg: #def7ec; --okInk: #0b6b4b; --badBg: #fde8e6; --badInk: #b03a2e; --midBg: #fff3d6; --midInk: #8a5a00;
}
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) {
  --bg: #0e1520; --card: #162130; --ink: #e3eaf3; --muted: #93a1b4; --line: #26354a; --soft: #1a2738; --hdr: #0a111b;
  --okBg: #113d2e; --okInk: #7fe0b8; --badBg: #4a1f1c; --badInk: #ffaba3; --midBg: #45360f; --midInk: #ffd27a; color-scheme: dark; } }
:root[data-theme="dark"] {
  --bg: #0e1520; --card: #162130; --ink: #e3eaf3; --muted: #93a1b4; --line: #26354a; --soft: #1a2738; --hdr: #0a111b;
  --okBg: #113d2e; --okInk: #7fe0b8; --badBg: #4a1f1c; --badInk: #ffaba3; --midBg: #45360f; --midInk: #ffd27a; color-scheme: dark; }

/* Trang riêng */
.page { margin: 0; min-height: 100%; background: var(--bg); color: var(--ink); font: 15px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; overflow: auto; display: block; }
.page header { background: var(--hdr); color: #fff; padding-block: 12px; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.page header .brand { font-size: 18px; font-weight: 700; }
.page header .sp { flex: 1; }
.page header a, .page header button { color: #dfe8f3; background: #263852; border: 0; border-radius: 8px; padding: 6px 12px; font: inherit; font-size: 14px; text-decoration: none; cursor: pointer; }
.wrap { max-width: 1200px; margin: 0 auto; padding-block: 20px; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 16px 18px; }
h1, h2, h3 { text-wrap: balance; margin: 0 0 10px; }
h2 { font-size: 18px; } h3 { font-size: 15px; }
label { display: grid; gap: 4px; font-size: 13px; color: var(--muted); }
input, textarea, select { font: inherit; color: var(--ink); background: var(--card); border: 1px solid var(--line); border-radius: 8px; padding: 8px 10px; }
textarea { min-height: 140px; resize: vertical; }
input:focus-visible, textarea:focus-visible, button:focus-visible, a:focus-visible { outline: 2px solid var(--blue); outline-offset: 2px; }
.btn { border: 0; border-radius: 9px; padding: 8px 14px; font: inherit; font-weight: 600; background: var(--blue); color: #fff; cursor: pointer; }
.btn.ghost { background: var(--soft); color: var(--ink); border: 1px solid var(--line); }
.btn.danger { background: var(--red); }
.btn.sm { padding: 5px 10px; font-size: 13px; }
.row { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.muted { color: var(--muted); font-size: 13px; }
.err { color: var(--badInk); background: var(--badBg); padding: 8px 10px; border-radius: 8px; font-size: 14px; }
.ok { color: var(--okInk); background: var(--okBg); padding: 8px 10px; border-radius: 8px; font-size: 14px; }

/* Đăng nhập */
.login { min-height: 100vh; display: grid; place-items: center; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); }
.login .card { width: min(420px, 100%); display: grid; gap: 12px; }
.login .logo { font-size: 26px; font-weight: 800; }
.switch { background: none; border: 0; color: var(--blue); cursor: pointer; font: inherit; font-size: 14px; padding: 0; justify-self: start; }

/* Giáo viên */
.tgrid { display: grid; grid-template-columns: 260px minmax(0, 1fr); gap: 16px; align-items: start; }
.classlist { display: grid; gap: 6px; }
.classlist button { text-align: left; border: 1px solid var(--line); background: var(--card); color: var(--ink); border-radius: 10px; padding: 10px 12px; cursor: pointer; font: inherit; }
.classlist button.on { border-color: var(--blue); box-shadow: inset 3px 0 0 var(--blue); }
.classlist small { display: block; color: var(--muted); }
.tabs2 { display: flex; gap: 4px; border-bottom: 1px solid var(--line); margin: 6px 0 14px; overflow-x: auto; }
.tabs2 button { border: 0; background: none; color: var(--muted); padding: 8px 12px; border-bottom: 2px solid transparent; font: inherit; cursor: pointer; white-space: nowrap; }
.tabs2 button.on { color: var(--ink); border-bottom-color: var(--blue); font-weight: 600; }
.code { font-family: ui-monospace, Consolas, monospace; font-size: 20px; letter-spacing: 3px; font-weight: 700; color: var(--blue); }
.tablewrap { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 14px; }
th, td { border-bottom: 1px solid var(--line); padding: 7px 8px; text-align: left; white-space: nowrap; }
th { font-size: 12px; color: var(--muted); font-weight: 600; letter-spacing: .02em; }
td.num { font-variant-numeric: tabular-nums; }
.cell { display: inline-flex; align-items: center; gap: 4px; padding: 3px 8px; border-radius: 8px; font-size: 13px; cursor: pointer; border: 0; font: inherit; font-size: 13px; }
.cell.solved { background: var(--okBg); color: var(--okInk); }
.cell.tried { background: var(--midBg); color: var(--midInk); }
.cell.none { background: transparent; color: var(--muted); cursor: default; }
.mono { font-family: ui-monospace, Consolas, monospace; }
@media (max-width: 760px) { .tgrid { grid-template-columns: 1fr; } }