/* AlphaForge Flashcards — forge-red theme (mirrors site/learn design tokens) */
:root {
  --bg: hsl(24 14% 5%);
  --surface: hsl(24 12% 9%);
  --surface-2: hsl(26 10% 13%);
  --surface-3: hsl(28 12% 18%);
  --border: hsl(30 10% 18%);
  --border-strong: hsl(30 10% 26%);
  --fg: hsl(38 30% 95%);
  --muted: hsl(36 12% 64%);
  --primary: hsl(12 90% 52%);
  --primary-soft: hsl(12 90% 52% / 0.14);
  --gold: #f59e0b;
  --ember: #f6501e;
  --again: #ef4444;
  --hard: #f59e0b;
  --good: #22c55e;
  --easy: #38bdf8;
  --radius: 0.85rem;
  --shadow: 0 8px 30px -8px rgb(239 69 31 / 0.18);
  --shadow-lg: 0 24px 70px -20px rgb(239 69 31 / 0.28);
  --mono: ui-monospace, "JetBrains Mono", "SF Mono", Menlo, monospace;
  --sans: "Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--sans);
  background:
    radial-gradient(1200px 600px at 85% -10%, hsl(12 90% 52% / 0.10), transparent 60%),
    radial-gradient(900px 500px at -5% 0%, hsl(38 90% 50% / 0.07), transparent 55%),
    var(--bg);
  color: var(--fg);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  line-height: 1.55;
}
a { color: var(--gold); text-decoration: none; }
a:hover { text-decoration: underline; }

.kicker {
  font-family: var(--mono);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.22em;
  color: var(--gold);
}

/* ---------- Top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 30;
  display: flex; align-items: center; gap: 1.25rem;
  padding: 0.85rem clamp(1rem, 4vw, 2.25rem);
  background: hsl(24 14% 5% / 0.82);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 0.6rem; font-weight: 800; letter-spacing: -0.02em; font-size: 1.05rem; }
.brand .flame {
  width: 1.7rem; height: 1.7rem; display: grid; place-items: center;
  background: linear-gradient(160deg, var(--gold), var(--primary));
  border-radius: 0.55rem; box-shadow: var(--shadow); font-size: 0.95rem;
}
.brand small { color: var(--muted); font-weight: 600; font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.18em; }
.modes { display: flex; gap: 0.25rem; margin-left: auto; background: var(--surface); padding: 0.25rem; border-radius: 0.7rem; border: 1px solid var(--border); }
.modes button {
  font: inherit; font-weight: 600; font-size: 0.85rem;
  color: var(--muted); background: transparent; border: 0; cursor: pointer;
  padding: 0.4rem 0.85rem; border-radius: 0.5rem; transition: 0.15s;
}
.modes button:hover { color: var(--fg); }
.modes button.active { background: var(--surface-3); color: var(--fg); box-shadow: inset 0 0 0 1px var(--border-strong); }

/* ---------- Layout ---------- */
.wrap { max-width: 1100px; margin: 0 auto; padding: clamp(1rem, 3vw, 2rem) clamp(1rem, 4vw, 2.25rem) 4rem; }

/* ---------- Filter bar ---------- */
.filters {
  display: flex; flex-wrap: wrap; gap: 0.6rem; align-items: center;
  margin-bottom: 1.4rem;
}
.filters .grow { flex: 1 1 220px; }
.field { position: relative; }
select, input[type="search"] {
  font: inherit; color: var(--fg); background: var(--surface);
  border: 1px solid var(--border); border-radius: 0.6rem;
  padding: 0.5rem 0.7rem; min-height: 2.4rem; width: 100%;
  appearance: none; transition: 0.15s;
}
select:focus, input:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-soft); }
select { padding-right: 2rem; cursor: pointer; }
.field.select::after {
  content: "▾"; position: absolute; right: 0.7rem; top: 50%; transform: translateY(-50%);
  color: var(--muted); pointer-events: none; font-size: 0.7rem;
}
input[type="search"]::-webkit-search-cancel-button { filter: invert(0.6); }
.chip-btn {
  font: inherit; font-weight: 600; font-size: 0.82rem; cursor: pointer;
  color: var(--muted); background: var(--surface); border: 1px solid var(--border);
  border-radius: 0.6rem; padding: 0.5rem 0.8rem; min-height: 2.4rem; transition: 0.15s;
  display: inline-flex; align-items: center; gap: 0.4rem; white-space: nowrap;
}
.chip-btn:hover { color: var(--fg); border-color: var(--border-strong); }
.chip-btn.on { color: var(--bg); background: var(--gold); border-color: var(--gold); }
.chip-btn.danger:hover { color: #fff; border-color: var(--again); background: hsl(0 84% 60% / 0.15); }

/* ---------- Study view ---------- */
.session-bar { display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; margin-bottom: 1rem; }
.counts { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.count { font-family: var(--mono); font-size: 0.72rem; padding: 0.28rem 0.55rem; border-radius: 0.45rem; border: 1px solid var(--border); color: var(--muted); }
.count b { color: var(--fg); }
.count.new b { color: var(--easy); }
.count.due b { color: var(--gold); }
.count.done b { color: var(--good); }
.progress { flex: 1 1 160px; height: 6px; border-radius: 999px; background: var(--surface-2); overflow: hidden; min-width: 120px; }
.progress > span { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--gold), var(--primary)); transition: width 0.35s; }

.stage { perspective: 1600px; }
.card {
  position: relative; width: 100%; min-height: 340px;
  cursor: pointer; transform-style: preserve-3d;
  transition: transform 0.5s cubic-bezier(0.4, 0.1, 0.2, 1);
}
.card.flipped { transform: rotateY(180deg); }
.face {
  position: absolute; inset: 0; backface-visibility: hidden; -webkit-backface-visibility: hidden;
  display: flex; flex-direction: column; padding: clamp(1.2rem, 3vw, 2.1rem);
  background: linear-gradient(180deg, var(--surface-2), var(--surface));
  border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow-lg);
  overflow-y: auto;
}
.face.back { transform: rotateY(180deg); background: linear-gradient(180deg, var(--surface), hsl(24 13% 7%)); }
.face .meta { display: flex; flex-wrap: wrap; gap: 0.4rem; align-items: center; margin-bottom: 1rem; }
.face .q { font-size: clamp(1.15rem, 2.6vw, 1.55rem); font-weight: 700; letter-spacing: -0.01em; }
.face .label-side { margin-top: auto; padding-top: 0.9rem; }
.face .a { font-size: clamp(0.98rem, 2vw, 1.08rem); white-space: pre-wrap; color: hsl(38 24% 90%); }
.face .a p { margin: 0 0 0.6rem; }
.flip-hint { margin-top: auto; padding-top: 1rem; color: var(--muted); font-size: 0.8rem; font-family: var(--mono); }

.badge {
  font-family: var(--mono); font-size: 0.66rem; text-transform: uppercase; letter-spacing: 0.08em;
  padding: 0.2rem 0.5rem; border-radius: 0.4rem; border: 1px solid var(--border-strong); color: var(--muted);
  white-space: nowrap;
}
.badge.cat { color: var(--gold); border-color: hsl(38 90% 50% / 0.4); background: hsl(38 90% 50% / 0.08); }
.badge.diff-Basic { color: var(--good); border-color: hsl(142 70% 45% / 0.4); }
.badge.diff-Advanced { color: var(--again); border-color: hsl(0 84% 60% / 0.4); }
.badge.diff-Mixed { color: var(--easy); border-color: hsl(199 89% 60% / 0.4); }
.badge.src { color: var(--muted); }
.star-btn { margin-left: auto; background: none; border: 0; cursor: pointer; font-size: 1.1rem; color: var(--surface-3); line-height: 1; }
.star-btn.on { color: var(--gold); }

.rating { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0.55rem; margin-top: 1rem; }
.rating button {
  font: inherit; font-weight: 700; cursor: pointer; color: var(--fg);
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 0.6rem;
  padding: 0.7rem 0.4rem; transition: 0.15s; display: flex; flex-direction: column; gap: 0.1rem; align-items: center;
}
.rating button:hover { transform: translateY(-2px); }
.rating button small { font-weight: 600; font-size: 0.66rem; color: var(--muted); font-family: var(--mono); }
.rating .again { border-bottom: 3px solid var(--again); }
.rating .hard { border-bottom: 3px solid var(--hard); }
.rating .good { border-bottom: 3px solid var(--good); }
.rating .easy { border-bottom: 3px solid var(--easy); }
.rating[hidden] { display: none; }

.empty { text-align: center; padding: 4rem 1rem; color: var(--muted); }
.empty h2 { color: var(--fg); margin-bottom: 0.5rem; }
.btn-primary {
  font: inherit; font-weight: 700; cursor: pointer; color: var(--bg);
  background: linear-gradient(160deg, var(--gold), var(--primary)); border: 0;
  border-radius: 0.6rem; padding: 0.65rem 1.2rem; margin-top: 1rem; box-shadow: var(--shadow);
}

/* ---------- Browse view ---------- */
.browse-count { color: var(--muted); font-size: 0.85rem; margin-bottom: 0.9rem; font-family: var(--mono); }
.bcard {
  background: var(--surface); border: 1px solid var(--border); border-radius: 0.7rem;
  margin-bottom: 0.6rem; overflow: hidden; transition: 0.15s;
}
.bcard:hover { border-color: var(--border-strong); }
.bcard > summary {
  list-style: none; cursor: pointer; padding: 0.85rem 1rem; display: flex; gap: 0.6rem; align-items: flex-start;
}
.bcard > summary::-webkit-details-marker { display: none; }
.bcard summary .q { font-weight: 650; flex: 1; }
.bcard[open] > summary { border-bottom: 1px solid var(--border); }
.bcard .body { padding: 0.9rem 1rem 1.1rem; white-space: pre-wrap; color: hsl(38 24% 88%); font-size: 0.95rem; }
.bcard .body .label-side { margin-top: 0.9rem; }
.tags { display: flex; flex-wrap: wrap; gap: 0.35rem; }
.tag { font-family: var(--mono); font-size: 0.66rem; color: var(--muted); border: 1px solid var(--border); border-radius: 0.4rem; padding: 0.15rem 0.45rem; }

/* ---------- Sources view ---------- */
.src-intro { color: var(--muted); margin-bottom: 1.3rem; max-width: 70ch; }
.src-grid { display: grid; gap: 0.8rem; }
.src {
  background: var(--surface); border: 1px solid var(--border); border-radius: 0.7rem; padding: 1rem 1.1rem;
  display: flex; gap: 1rem; align-items: flex-start; flex-wrap: wrap;
}
.src .icon { font-size: 1.4rem; }
.src .info { flex: 1 1 260px; }
.src .info h3 { font-size: 1rem; margin-bottom: 0.2rem; }
.src .info p { color: var(--muted); font-size: 0.85rem; }
.src .info .cats { margin-top: 0.5rem; }
.src .stat { text-align: right; font-family: var(--mono); }
.src .stat .n { font-size: 1.5rem; font-weight: 800; color: var(--gold); }
.src .stat .l { font-size: 0.66rem; text-transform: uppercase; letter-spacing: 0.12em; color: var(--muted); }
.status { font-family: var(--mono); font-size: 0.64rem; text-transform: uppercase; letter-spacing: 0.1em; padding: 0.18rem 0.5rem; border-radius: 0.4rem; }
.status.carded { color: var(--good); background: hsl(142 70% 45% / 0.12); }
.status.indexed { color: var(--muted); background: var(--surface-2); }

.foot { margin-top: 2.5rem; padding-top: 1.2rem; border-top: 1px solid var(--border); color: var(--muted); font-size: 0.78rem; display: flex; justify-content: space-between; flex-wrap: wrap; gap: 0.5rem; }

@media (max-width: 560px) {
  .modes { width: 100%; margin-left: 0; }
  .modes button { flex: 1; }
  .rating { grid-template-columns: repeat(2, 1fr); }
  .face { min-height: 0; }
  .card { min-height: 380px; }
}
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); border: 0; }