:root {
  --bg: #f4f1ea;
  --panel: #ffffff;
  --ink: #1f2933;
  --muted: #6b7280;
  --line: #e5e0d5;
  --accent: #2f5d50;
  --accent-ink: #ffffff;
  --again: #c0392b;
  --hard: #d98e04;
  --good: #2f8f5b;
  --easy: #2e6fd8;
  --ok: #2f8f5b;
  --bad: #c0392b;
  --radius: 12px;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; background: var(--bg); color: var(--ink); line-height: 1.45; }
a { color: var(--accent); }
h1 { font-size: 1.5rem; margin: 0 0 .5rem; }
h2 { font-size: 1.1rem; margin: 0 0 .5rem; }
.muted { color: var(--muted); }
.small { font-size: .85rem; }
.ok { color: var(--ok); }
.bad { color: var(--bad); }
.hidden { display: none !important; }
kbd { font: inherit; font-size: .7em; border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 4px; padding: 0 .35em; color: var(--muted); background: #fafafa; margin-left: .35em; }

.top { display: flex; align-items: center; justify-content: space-between; padding: .6rem 1rem; background: #1f2933; color: #fff; }
.top a { color: #fff; text-decoration: none; }
.top nav a { margin-left: 1rem; opacity: .85; }
.brand { font-weight: 700; font-size: 1.05rem; }
.flash { background: #fff8db; border-bottom: 1px solid #f1e3a2; padding: .5rem 1rem; }
.wrap { max-width: 1100px; margin: 0 auto; padding: 1rem; }

.card { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 1rem; margin-bottom: 1rem; }
.card.narrow { max-width: 380px; margin: 3rem auto; }
.btn { display: inline-block; border: 1px solid var(--line); background: #fff; color: var(--ink); border-radius: 999px; padding: .5rem 1rem; font: inherit; cursor: pointer; text-decoration: none; }
.btn:hover { border-color: #c9c2b4; }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn.small { padding: .3rem .75rem; font-size: .85rem; }
.btn.danger { color: var(--bad); }
.btn:disabled { opacity: .5; cursor: default; }
.row { display: flex; gap: .5rem; align-items: center; flex-wrap: wrap; margin: .5rem 0; }
label { display: block; font-size: .9rem; margin: .5rem 0; }
input[type=text], input[type=password], input[type=number], input:not([type]), select, textarea { width: 100%; font: inherit; padding: .45rem .6rem; border: 1px solid var(--line); border-radius: 8px; background: #fff; }
textarea { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .85rem; }
.grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0 1rem; }
.grid .full { grid-column: 1 / -1; }
.grid.compact label { margin: .25rem 0; font-size: .8rem; }

/* decks */
.decks { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 1rem; }
.deck-head { display: flex; gap: .75rem; align-items: flex-start; }
.swatch { width: 22px; height: 22px; border-radius: 6px; border: 2px solid #1f2933; flex: none; margin-top: .2rem; }
.swatch.white { background: #fff; }
.swatch.black { background: #1f2933; }
.counts { display: grid; grid-template-columns: repeat(4, 1fr); gap: .5rem; margin: 1rem 0; text-align: center; }
.counts b { display: block; font-size: 1.4rem; }
.counts span { font-size: .75rem; color: var(--muted); }
.counts .due { color: var(--good); }
.counts .learn { color: var(--again); }
.counts .new { color: var(--easy); }
.actions { display: flex; gap: .5rem; }
.deck-foot { margin-top: .75rem; }
.danger-zone { margin-top: .5rem; }
.danger-zone form { display: inline-block; margin: .25rem .25rem 0 0; }

/* study + tree layout */
.study, .tree-page { display: grid; grid-template-columns: minmax(280px, 560px) minmax(300px, 1fr); gap: 1.5rem; align-items: start; }
.board-col { position: sticky; top: 1rem; }
/* Board coordinates: bigger, bold, dark with a light halo so they read on both square colours. */
.cg-wrap coords { opacity: 1; font-size: 14px; font-weight: 700; }
.cg-wrap coords coord { color: #2a2118 !important; text-shadow: 0 0 2px #fff, 0 0 3px #fff, 0 1px 4px rgba(255,255,255,.95); }
.cg-wrap coords.files { bottom: 1px; }
.cg-wrap { width: 100%; aspect-ratio: 1 / 1; border-radius: 6px; overflow: hidden; box-shadow: 0 6px 20px rgba(0,0,0,.15); }
.under-board { display: flex; justify-content: space-between; align-items: center; margin-top: .6rem; min-height: 1.6rem; }
.status { font-weight: 600; }
.status.correct { color: var(--good); }
.status.wrong { color: var(--again); }
.counts-inline { font-size: .85rem; color: var(--muted); }
.counts-inline b { color: var(--ink); }
.panel-head { display: flex; justify-content: space-between; align-items: baseline; gap: 1rem; }
.line { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .95rem; margin: .5rem 0; word-break: break-word; }
.line .mv { padding: 0 .1em; }
.line .mv.ours { font-weight: 700; }
.line .mv.last { background: #fff3c4; border-radius: 4px; }
.line .num { color: var(--muted); margin-left: .4em; }
.chip { display: inline-block; font-size: .7rem; font-weight: 600; text-transform: uppercase; letter-spacing: .04em; padding: .1rem .5rem; border-radius: 999px; background: #eee; color: #555; vertical-align: middle; }
.chip.new { background: #dbe8ff; color: #1d4ed8; }
.chip.learning, .chip.relearning { background: #ffe1dc; color: #b42318; }
.chip.review { background: #dcf3e6; color: #1b6b3a; }
.chip.running { background: #fff3c4; color: #7a5a00; }
.chip.done { background: #dcf3e6; color: #1b6b3a; }
.chip.error { background: #ffe1dc; color: #b42318; }
.prompt { margin-top: 1rem; }
.verdict { font-size: 1.2rem; font-weight: 700; margin: .75rem 0 .5rem; }
.verdict.correct { color: var(--good); }
.verdict.wrong { color: var(--again); }
.why { margin-bottom: .75rem; }
.why-line { font-size: 1.02rem; line-height: 1.45; margin: 0 0 .6rem; padding: .55rem .75rem; background: #fff6e8; border-left: 3px solid var(--again); border-radius: 6px; }
.why-line.pending { color: var(--muted); font-style: italic; background: transparent; border-left-color: var(--line); }
.why-line.failed { color: var(--muted); background: transparent; border-left-color: var(--line); }
.why-line .retry { margin-left: .4rem; }
.note { background: #f7f5ef; border-left: 3px solid var(--accent); padding: .5rem .75rem; border-radius: 6px; margin: .5rem 0; font-size: .92rem; }
.alts { width: 100%; border-collapse: collapse; font-size: .85rem; margin-top: .5rem; }
.alts th, .alts td { text-align: left; padding: .25rem .4rem; border-bottom: 1px solid var(--line); }
.alts tr.chosen td { font-weight: 700; background: #f0f7f3; }
.alts tr.played td { background: #fff3f0; }
.alts .bar { display: flex; height: 10px; border-radius: 3px; overflow: hidden; min-width: 90px; }
.alts .bar i { display: block; height: 100%; }
.alts .bar .w { background: #f5f5f5; border: 1px solid #ddd; }
.alts .bar .d { background: #bbb; }
.alts .bar .b { background: #333; }
.ratings { display: grid; grid-template-columns: repeat(4, 1fr); gap: .5rem; margin: .75rem 0; }
.rate { display: flex; flex-direction: column; align-items: center; padding: .5rem .25rem; border-width: 2px; }
.rate small { color: var(--muted); font-size: .75rem; }
.rate kbd { margin: .15rem 0 0; }
.rate.again { border-color: var(--again); }
.rate.hard { border-color: var(--hard); }
.rate.good { border-color: var(--good); }
.rate.easy { border-color: var(--easy); }
.keys { margin-top: 1.5rem; }
.done { margin-top: 1rem; }

/* tree */
.tree { font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .85rem; max-height: 70vh; overflow: auto; background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: .5rem; }
.tree ul { list-style: none; margin: 0; padding-left: 1rem; border-left: 1px dotted #d7d0c2; }
.tree > ul { padding-left: 0; border: none; }
.tree li { margin: .05rem 0; }
.tree .n { display: inline-flex; align-items: center; gap: .35rem; padding: .05rem .35rem; border-radius: 4px; cursor: pointer; }
.tree .n:hover { background: #f3efe6; }
.tree .n.sel { background: #dcf3e6; }
.tree .n.ours .san { font-weight: 700; }
.tree .n .st { color: var(--muted); font-size: .75rem; }
.tree .tg { width: 1rem; display: inline-block; text-align: center; color: var(--muted); cursor: pointer; user-select: none; }
.tree .dot { width: 7px; height: 7px; border-radius: 50%; display: inline-block; }
.tree .dot.new { background: #1d4ed8; }
.tree .dot.learning, .tree .dot.relearning { background: #b42318; }
.tree .dot.review { background: #1b6b3a; }
.tree li.collapsed > ul { display: none; }
.tree-tools { justify-content: flex-end; }
.tree-tools .muted { margin-right: auto; }
.sel-panel { margin-top: .75rem; }
.sel-panel .alts td:last-child { text-align: right; }
.build .row { margin-bottom: 0; }
progress { width: 100%; }

@media (max-width: 820px) {
  .study, .tree-page { grid-template-columns: 1fr; }
  .board-col { position: static; }
  .cg-wrap { max-width: 92vw; margin: 0 auto; }
  .wrap { padding: .75rem; }
  .grid { grid-template-columns: 1fr; }
  .keys { display: none; }
}