:root {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
  color-scheme: light;
  --page-bg: #fff;
  --text: #111;
  --muted: #555;
  --label: #333;
  --link: #0d6efd;
  --border: #ddd;
  --soft-border: #eee;
  --control-border: #ccc;
  --surface: #fff;
  --surface-soft: #fafafa;
  --surface-muted: #f6f6f6;
  --success-soft: #eef7ee;
  --primary-bg: #111;
  --primary-hover: #333;
  --primary-text: #fff;
  --ok: #0a7b33;
  --bad: #b00020;
}

html[data-theme="dark"],
body.theme-dark {
  color-scheme: dark;
  --page-bg: #111318;
  --text: #f1f3f5;
  --muted: #adb5bd;
  --label: #d7dce2;
  --link: #8ab4ff;
  --border: #3a404a;
  --soft-border: #2b3038;
  --control-border: #4a515d;
  --surface: #191c22;
  --surface-soft: #232832;
  --surface-muted: #252b34;
  --success-soft: #163623;
  --primary-bg: #f1f3f5;
  --primary-hover: #d7dce2;
  --primary-text: #111318;
  --ok: #6ee7a8;
  --bad: #ff8a9a;
}

body {
  max-width: 900px; margin: 24px auto; padding: 0 16px;
  background: var(--page-bg); color: var(--text);
}
h1 { font-size: 22px; margin: 0 0 16px; }
a { color: var(--link); text-decoration: none; }
a:hover { text-decoration: underline; }
.site-header {
  display: flex; justify-content: space-between; align-items: center;
  padding-bottom: 12px; border-bottom: 1px solid var(--soft-border); margin-bottom: 20px;
}
.brand { font-weight: 700; font-size: 18px; color: var(--text); }
.site-header nav { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; justify-content: flex-end; }
.site-header nav a, .site-header nav .linkish { margin-left: 6px; }
.nav-pill {
  display: inline-flex; align-items: center; min-height: 34px; padding: 0 12px;
  border: 1px solid var(--border); border-radius: 8px; color: var(--text); background: var(--surface);
}
.nav-pill:hover { text-decoration: none; border-color: var(--control-border); }
.nav-pill.is-active { background: var(--primary-bg); border-color: var(--primary-bg); color: var(--primary-text); }
.linkish {
  background: none; border: none; padding: 0; color: var(--link); cursor: pointer;
  font: inherit;
}
.inline-form { display: inline; }
.exercises { padding-left: 20px; }
.auth-form { display: flex; flex-direction: column; gap: 12px; max-width: 320px; }
.auth-form label { display: flex; flex-direction: column; gap: 4px; font-size: 14px; }
.auth-form input {
  padding: 8px 10px; border: 1px solid var(--control-border); border-radius: 8px; font-size: 14px;
}
button.primary {
  background: var(--primary-bg); color: var(--primary-text); border: 1px solid var(--primary-bg); padding: 8px 14px;
  border-radius: 8px; cursor: pointer;
}
button.primary:hover { background: var(--primary-hover); }
.error { color: var(--bad); }
.stats-table { border-collapse: collapse; margin-top: 8px; font-size: 14px; }
.stats-table th, .stats-table td {
  border: 1px solid var(--border); padding: 6px 10px; text-align: right;
}
.stats-table th { background: var(--surface-muted); text-align: center; }
.stats-table td:first-child { text-align: left; }
.stats-block { margin-bottom: 24px; }
.stats-table.confusion td, .stats-table.confusion th { text-align: center; min-width: 34px; }
.stats-table.confusion caption { font-size: 12px; color: var(--muted); text-align: left; caption-side: top; padding: 0 0 4px; }
.stats-table.confusion td.diag { background: var(--success-soft); font-weight: 600; }
.stats-table.confusion td.zero { color: var(--muted); }
.stats-table.confusion td.empty { color: var(--muted); }
.stats-table.confusion tr.totals td, .stats-table.confusion tr.totals th { background: var(--surface-soft); color: var(--muted); font-size: 12px; }
.stats-table.leaderboard td:nth-child(2) { text-align: left; }

.stats-tabs { display: flex; gap: 4px; border-bottom: 1px solid var(--soft-border); margin: 0 0 16px; }
.stats-tab {
  padding: 8px 14px; border: 1px solid transparent; border-bottom: none;
  border-radius: 8px 8px 0 0; color: var(--muted); font-size: 14px;
  margin-bottom: -1px;
}
.stats-tab:hover { text-decoration: none; color: var(--text); background: var(--surface-soft); }
.stats-tab.is-active {
  color: var(--text); background: var(--surface); border-color: var(--soft-border); font-weight: 600;
}

.period-tabs { display: flex; flex-wrap: wrap; gap: 6px; margin: 0 0 14px; }
.period-tab {
  padding: 5px 12px; border: 1px solid var(--border); border-radius: 999px;
  background: var(--surface-soft); color: var(--label); font-size: 13px; cursor: pointer;
}
.period-tab:hover { border-color: var(--control-border); }
.period-tab.is-active {
  background: var(--primary-bg); border-color: var(--primary-bg); color: var(--primary-text);
}

.history-list { padding-left: 20px; list-style: none; margin: 6px 0 0; }
.history-list li { margin: 2px 0; }

.theme-toggle {
  display: inline-flex; align-items: center; gap: 8px; min-height: 36px;
  padding: 0 10px; border: 1px solid var(--border); border-radius: 10px;
  background: var(--surface-soft); color: var(--label); white-space: nowrap;
  cursor: pointer; user-select: none;
}
.theme-toggle input {
  position: absolute; inline-size: 1px; block-size: 1px; overflow: hidden;
  clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap;
}
.theme-toggle-track {
  --toggle-track-width: 42px;
  --toggle-track-height: 24px;
  --toggle-thumb-size: 18px;
  --toggle-thumb-offset: 2px;
  box-sizing: border-box; position: relative; flex: 0 0 auto;
  inline-size: var(--toggle-track-width); block-size: var(--toggle-track-height);
  border: 1px solid var(--control-border); border-radius: 999px;
  background: var(--surface); transition: background 160ms ease, border-color 160ms ease;
}
.theme-toggle-track::before {
  content: ""; position: absolute;
  inset-block-start: var(--toggle-thumb-offset);
  inset-inline-start: var(--toggle-thumb-offset);
  inline-size: var(--toggle-thumb-size); block-size: var(--toggle-thumb-size); border-radius: 50%;
  background: var(--muted); box-shadow: 0 1px 2px rgba(0, 0, 0, .22);
  transition: transform 160ms ease, background 160ms ease;
}
.theme-toggle input:checked + .theme-toggle-track {
  background: var(--primary-bg); border-color: var(--primary-bg);
}
.theme-toggle input:checked + .theme-toggle-track::before {
  transform: translateX(calc(
    var(--toggle-track-width) - var(--toggle-thumb-size) - var(--toggle-thumb-offset) * 2 - 2px
  ));
  background: var(--primary-text);
}
.theme-toggle input:focus-visible + .theme-toggle-track {
  outline: 2px solid var(--link); outline-offset: 2px;
}
.theme-toggle-nav {
  min-height: 34px;
}
.card { border: 1px solid var(--border); border-radius: 12px; padding: 14px; margin: 12px 0; background: var(--surface); }
.row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
label { font-size: 13px; color: var(--label); }
select, input:not([type="submit"]):not([type="button"]), button {
  font-size: 14px; padding: 8px 10px; border-radius: 10px; border: 1px solid var(--control-border);
  background: var(--surface-soft); color: var(--text);
}
button { cursor: pointer; background: var(--surface-soft); }
button.primary { background: var(--primary-bg); color: var(--primary-text); border-color: var(--primary-bg); }
.small { font-size: 12px; color: var(--muted); }
.status { font-size: 14px; }
.ok { color: var(--ok); }
.bad { color: var(--bad); }
.mono { font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace; }
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.chord-toggles { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px; padding: 6px 10px;
  border: 1px solid var(--border); border-radius: 999px; background: var(--surface-soft);
}
.chip input { margin: 0; }
.answer-toolbar { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.answer-btn {
  min-width: 74px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
}
.answer-btn .root { display: block; font-size: 12px; color: var(--muted); margin-top: 2px; }
@media (max-width: 720px) {
  .grid2 { grid-template-columns: 1fr; }
  .site-header { align-items: flex-start; }
  .site-header nav { justify-content: flex-start; }
  .theme-toggle-nav { flex-basis: 100%; justify-content: space-between; }
}