:root {
  --bg: #f6f7fa; --card: #ffffff; --fg: #1d2330; --muted: #5d6576; --line: #c9cfdb;
  --accent: #3866c7; --accent-fg: #ffffff; --ok-bg: #eaf6ec; --ok: #2e7d3a; --err-bg: #fdecec; --err: #b42318;
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15181f; --card: #1d212a; --fg: #e6e9ef; --muted: #a2a9b8; --line: #3a404d;
    --accent: #7fa6f0; --accent-fg: #10131a; --ok-bg: #183020; --ok: #7cc985; --err-bg: #3a1d1d; --err: #f08a7e;
  }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--fg); font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
.top { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 24px; padding: 12px 20px; border-bottom: 1px solid var(--line); background: var(--card); }
.top h1 { font-size: 20px; margin: 0; }
.top nav { display: flex; flex-wrap: wrap; gap: 6px; }
.top nav a { color: var(--fg); text-decoration: none; padding: 6px 12px; border-radius: 8px; border: 1px solid transparent; }
.top nav a[aria-current="page"] { border-color: var(--accent); color: var(--accent); font-weight: 600; }
main { max-width: 960px; margin: 0 auto; padding: 20px; }
main:focus { outline: none; }
.screen { display: grid; gap: 16px; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 16px 20px; }
.card h2 { font-size: 18px; margin: 0 0 12px; }
.field { display: grid; gap: 4px; margin-bottom: 12px; }
.field span { font-size: 14px; color: var(--muted); }
input { font: inherit; color: inherit; background: var(--bg); border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; min-height: 44px; }
input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
button { font: inherit; min-height: 44px; padding: 8px 18px; border-radius: 8px; border: 1px solid var(--accent); background: var(--accent); color: var(--accent-fg); cursor: pointer; font-weight: 600; }
button.secondary { background: transparent; color: var(--accent); }
button:disabled { opacity: 0.45; cursor: not-allowed; }
.msg { margin: 12px 0 0; padding: 0; min-height: 1.5em; }
.msg[data-kind="ok"] { background: var(--ok-bg); color: var(--ok); padding: 8px 12px; border-radius: 8px; }
.msg[data-kind="error"] { background: var(--err-bg); color: var(--err); padding: 8px 12px; border-radius: 8px; }
.muted { color: var(--muted); margin: 0 0 8px; }
.list { width: 100%; border-collapse: collapse; font-size: 15px; }
.list th, .list td { text-align: left; padding: 8px; border-bottom: 1px solid var(--line); vertical-align: top; }
.list th { color: var(--muted); font-weight: 600; font-size: 14px; }
.list .num { text-align: right; white-space: nowrap; }
.narrow { max-width: 440px; }
.student-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 16px; background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 10px 16px; }
.student-bar .hello { font-weight: 600; }
.student-bar .count { color: var(--muted); }
.student-bar button { margin-left: auto; }
input[type="search"] { width: 100%; }
[hidden] { display: none !important; }
@media (max-width: 560px) { main { padding: 12px; } .card { padding: 12px; } }