/* Math Practice v2 — design system.
   Modern/tech: Inter variable, deep-navy dark base, indigo→cyan accent,
   glass cards. Light theme via prefers-color-scheme. */

@font-face {
  font-family: 'Inter Variable';
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url('../vendor/fonts/inter-latin-wght-normal.woff2') format('woff2-variations');
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }

:root {
  --font: 'Inter Variable', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --accent-1: #6366f1;
  --accent-2: #22d3ee;
  --accent-grad: linear-gradient(135deg, var(--accent-1), var(--accent-2));
  --ok: #34d399;
  --ok-ink: #065f46;
  --bad: #fb7185;
  --bad-ink: #9f1239;
  --warn: #fbbf24;
  --radius: 14px;

  --bg: #f4f6fb;
  --bg-glow: radial-gradient(1200px 600px at 80% -10%, rgba(99, 102, 241, 0.12), transparent 60%),
             radial-gradient(900px 500px at -10% 110%, rgba(34, 211, 238, 0.10), transparent 60%);
  --card: #ffffff;
  --card-border: #e3e7f2;
  --ink: #171c2e;
  --muted: #5d647b;
  --input-bg: #ffffff;
  --input-border: #ccd3e4;
  --track: #e3e7f2;
  --ok-bg: #e7f9f1;
  --bad-bg: #ffe9ed;
  --warn-bg: #fdf3d8;
  --warn-ink: #7a5b00;
  --shadow: 0 10px 30px rgba(23, 28, 46, 0.08);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1020;
    --bg-glow: radial-gradient(1200px 600px at 80% -10%, rgba(99, 102, 241, 0.22), transparent 60%),
               radial-gradient(900px 500px at -10% 110%, rgba(34, 211, 238, 0.12), transparent 60%);
    --card: rgba(255, 255, 255, 0.045);
    --card-border: rgba(255, 255, 255, 0.09);
    --ink: #e8ebf5;
    --muted: #8b93ab;
    --input-bg: rgba(255, 255, 255, 0.06);
    --input-border: rgba(255, 255, 255, 0.16);
    --track: rgba(255, 255, 255, 0.10);
    --ok-bg: rgba(52, 211, 153, 0.14);
    --ok-ink: #6ee7b7;
    --bad-bg: rgba(251, 113, 133, 0.14);
    --bad-ink: #fda4af;
    --warn-bg: rgba(251, 191, 36, 0.12);
    --warn-ink: #fcd34d;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  }
}

html { font-size: 16px; }

body {
  margin: 0;
  min-height: 100dvh;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  background-image: var(--bg-glow);
  background-attachment: fixed;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

.shell { max-width: 680px; margin: 0 auto; padding: 1.25rem 1rem 3rem; }
.shell.wide { max-width: 1040px; }

h1, h2, h3 { line-height: 1.25; margin: 0 0 0.5rem; letter-spacing: -0.02em; }
h1 { font-size: 1.7rem; font-weight: 750; }
h2 { font-size: 1.25rem; font-weight: 700; }
h3 { font-size: 1.05rem; font-weight: 650; }
p { margin: 0.4rem 0; }
a { color: var(--accent-1); }

.brand {
  display: inline-flex; align-items: center; gap: 0.5rem;
  font-weight: 800; letter-spacing: -0.02em; font-size: 1.05rem;
}
.brand .logo {
  width: 28px; height: 28px; border-radius: 8px;
  background: var(--accent-grad);
  display: inline-flex; align-items: center; justify-content: center;
  color: #fff; font-size: 15px; font-weight: 800;
}
.grad-text {
  background: var(--accent-grad);
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent; color: transparent;
}
.subtitle { color: var(--muted); margin-top: 0; }

/* ---- Cards ---- */
.card {
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: var(--radius);
  padding: 1.4rem;
  box-shadow: var(--shadow);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
}
.card + .card { margin-top: 1rem; }

/* ---- Buttons ---- */
button { font: inherit; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem;
  font-weight: 650; font-size: 1rem;
  padding: 0.65rem 1.3rem;
  border: none; border-radius: 10px;
  background: var(--accent-grad);
  color: #fff; cursor: pointer;
  transition: transform 0.08s ease, filter 0.15s ease;
}
.btn:hover { filter: brightness(1.08); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: 0.55; cursor: default; }
.btn.block { display: flex; width: 100%; }
.btn.ghost {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--input-border);
}
.btn.ghost:hover { border-color: var(--accent-1); filter: none; }
.btn.danger { background: linear-gradient(135deg, #f43f5e, #fb7185); }
.btn.small { font-size: 0.85rem; padding: 0.35rem 0.8rem; border-radius: 8px; }
.link-btn {
  background: none; border: none; color: var(--accent-1);
  padding: 0.25rem 0; cursor: pointer; font: inherit;
}

/* ---- Forms ---- */
label { display: block; font-weight: 600; font-size: 0.92rem; margin: 0.9rem 0 0.3rem; }
input[type="text"], input[type="email"], input[type="password"], input[type="number"],
input[type="date"], select, textarea {
  width: 100%;
  font: inherit; font-size: 1rem;
  color: var(--ink);
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 10px;
  padding: 0.6rem 0.8rem;
}
textarea { resize: vertical; min-height: 90px; }
input:focus, select:focus, textarea:focus {
  outline: 2px solid var(--accent-1);
  outline-offset: 1px;
  border-color: transparent;
}
.field-row { display: flex; gap: 0.8rem; flex-wrap: wrap; }
.field-row > div { flex: 1; min-width: 130px; }
.hint { color: var(--muted); font-size: 0.85rem; margin-top: 0.25rem; }

/* ---- Badges ---- */
.badge {
  display: inline-flex; align-items: center;
  font-size: 0.75rem; font-weight: 650;
  padding: 0.12rem 0.6rem; border-radius: 999px;
  border: 1px solid var(--card-border);
  color: var(--muted); white-space: nowrap;
}
.badge.ok { background: var(--ok-bg); color: var(--ok-ink); border-color: transparent; }
.badge.bad { background: var(--bad-bg); color: var(--bad-ink); border-color: transparent; }
.badge.warn { background: var(--warn-bg); color: var(--warn-ink); border-color: transparent; }
.badge.accent { background: var(--accent-grad); color: #fff; border-color: transparent; }

/* ---- Feedback banners ---- */
.feedback { margin-top: 1rem; padding: 0.9rem 1.1rem; border-radius: 10px; }
.feedback.correct { background: var(--ok-bg); color: var(--ok-ink); }
.feedback.wrong { background: var(--bad-bg); color: var(--bad-ink); }
.feedback.nudge { background: var(--warn-bg); color: var(--warn-ink); }
.feedback .fb-line { margin: 0.25rem 0; overflow-x: auto; }
.feedback .fb-head { font-weight: 750; }

/* ---- Progress ring (drill) ---- */
.ring-wrap { display: flex; align-items: center; gap: 0.9rem; }
.ring { width: 62px; height: 62px; transform: rotate(-90deg); }
.ring .track { fill: none; stroke: var(--track); stroke-width: 6; }
.ring .fill {
  fill: none; stroke: url(#ringGrad); stroke-width: 6; stroke-linecap: round;
  transition: stroke-dashoffset 0.45s cubic-bezier(0.22, 1, 0.36, 1);
}
.ring-label { font-weight: 750; font-variant-numeric: tabular-nums; font-size: 1.05rem; }
.ring-sub { color: var(--muted); font-size: 0.82rem; }

/* ---- Drill specifics ---- */
.prompt { font-size: 1.12rem; margin-bottom: 1rem; overflow-x: auto; }
.prompt .katex-display { margin: 0.6rem 0; }
.choice {
  display: flex; align-items: center; gap: 0.6rem;
  border: 1px solid var(--input-border); border-radius: 10px;
  padding: 0.65rem 0.8rem; cursor: pointer; margin-bottom: 0.5rem;
  background: var(--input-bg);
}
.choice:has(input:checked) { border-color: var(--accent-1); outline: 1px solid var(--accent-1); }
.choice input { width: 1.05rem; height: 1.05rem; accent-color: var(--accent-1); }

/* ---- Admin layout ---- */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  gap: 1rem; flex-wrap: wrap; margin-bottom: 1.2rem;
}
.nav { display: flex; gap: 0.25rem; flex-wrap: wrap; }
.nav button {
  background: none; border: none; cursor: pointer;
  color: var(--muted); font-weight: 650; font-size: 0.95rem;
  padding: 0.45rem 0.9rem; border-radius: 999px;
}
.nav button.active { background: var(--accent-grad); color: #fff; }
.nav button:not(.active):hover { color: var(--ink); }

.table-wrap { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 0.93rem; }
th, td { text-align: left; padding: 0.55rem 0.7rem; border-bottom: 1px solid var(--card-border); vertical-align: top; }
th { color: var(--muted); font-weight: 650; font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.04em; }
tr.clickable { cursor: pointer; }
tr.clickable:hover td { background: rgba(99, 102, 241, 0.06); }

.list-item {
  display: flex; align-items: center; justify-content: space-between; gap: 0.8rem;
  padding: 0.85rem 0; border-bottom: 1px solid var(--card-border); flex-wrap: wrap;
}
.list-item:last-child { border-bottom: none; }
.item-meta { color: var(--muted); font-size: 0.86rem; display: flex; gap: 0.55rem; flex-wrap: wrap; align-items: center; }

.mark-correct { color: var(--ok-ink); font-weight: 750; }
.mark-wrong { color: var(--bad-ink); font-weight: 750; }
.mark-none { color: var(--muted); }

.error-panel {
  background: var(--bad-bg); color: var(--bad-ink);
  border-radius: 10px; padding: 1rem;
  white-space: pre-wrap; word-break: break-word;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 0.88rem;
}

.toast {
  position: fixed; left: 50%; bottom: 1.4rem; transform: translateX(-50%);
  background: var(--ink); color: var(--bg);
  padding: 0.6rem 1.1rem; border-radius: 999px;
  font-weight: 650; font-size: 0.92rem;
  box-shadow: var(--shadow); z-index: 50;
  opacity: 0; pointer-events: none; transition: opacity 0.25s ease;
}
.toast.show { opacity: 1; }

/* ---- Help / docs ---- */
.help details {
  border: 1px solid var(--card-border);
  border-radius: 10px;
  padding: 0.55rem 0.9rem;
  margin-top: 0.7rem;
}
.help summary { cursor: pointer; padding: 0.25rem 0; }
.help summary:hover { color: var(--accent-1); }
.help details[open] summary { margin-bottom: 0.35rem; }
.help p, .help li { font-size: 0.94rem; }
.help ul, .help ol { margin: 0.4rem 0; padding-left: 1.3rem; }
.help li { margin: 0.3rem 0; }
.help code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.85em;
  background: var(--input-bg);
  border: 1px solid var(--card-border);
  border-radius: 5px;
  padding: 0.05rem 0.35rem;
}
.help .math-demo { display: inline-block; }
.help .math-demo .katex-display { display: inline-block; margin: 0 0 0 0.3rem; }

.center { text-align: center; }
.mt { margin-top: 1rem; }
.row { display: flex; gap: 0.6rem; align-items: center; flex-wrap: wrap; }
.spread { justify-content: space-between; }
.muted { color: var(--muted); }
.mono { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 0.86em; }