:root {
  --bg: #f6f4ef;
  --surface: #ffffff;
  --ink: #1f2328;
  --muted: #6b6f76;
  --line: #e3dfd6;
  --accent: #23606e;
  --accent-ink: #ffffff;
  --accent-soft: #e3eff1;
  --new: #2563eb;
  --learn: #c2410c;
  --due: #15803d;
  --again: #b42318;
  --hard: #9a6700;
  --good: #1a7f37;
  --easy: #2457b8;
  --radius: 10px;
  --shadow: 0 1px 2px rgba(20, 20, 20, .05), 0 4px 16px rgba(20, 20, 20, .04);
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", sans-serif;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 15px/1.5 var(--sans); }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
h1 { font-size: 1.6rem; margin: 0 0 .75rem; letter-spacing: -.01em; }
h2 { font-size: 1.05rem; margin: 0 0 .6rem; }
code, kbd { font-family: var(--mono); font-size: .85em; }
code { background: #efece4; padding: .05em .35em; border-radius: 4px; }
kbd { border: 1px solid currentColor; border-radius: 4px; padding: 0 .3em; opacity: .55; font-size: .7em; margin-left: .35em; }
.muted { color: var(--muted); }
.small { font-size: .85rem; }

.topbar { display: flex; align-items: center; gap: 1.5rem; padding: .7rem 1.5rem; background: var(--surface); border-bottom: 1px solid var(--line); position: sticky; top: 0; z-index: 5; }
.brand { font-weight: 700; color: var(--ink); font-size: 1.1rem; letter-spacing: -.01em; }
.brand-mark { color: var(--accent); }
.topbar nav { display: flex; gap: .2rem; flex: 1; flex-wrap: wrap; }
.topbar nav a { color: var(--muted); padding: .35rem .7rem; border-radius: 7px; }
.topbar nav a:hover { background: var(--bg); text-decoration: none; color: var(--ink); }
.topbar nav a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.who { display: flex; gap: .6rem; align-items: center; color: var(--muted); margin: 0; }

.page { max-width: 1100px; margin: 0 auto; padding: 1.5rem; }
.page-head { display: flex; justify-content: space-between; align-items: center; gap: 1rem; flex-wrap: wrap; margin-bottom: .75rem; }
.page-head h1, .page-head h2 { margin: 0; }
.actions { display: flex; gap: .5rem; flex-wrap: wrap; align-items: center; }
.actions form { margin: 0; }

.panel { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 1.1rem 1.25rem; box-shadow: var(--shadow); margin-bottom: 1rem; }
.grid2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 1rem; }
.grid2 > .panel { margin-bottom: 0; }
.grid2 + .panel, .panel + .grid2 { margin-top: 1rem; }
.narrow { max-width: 560px; }
.stack > * + * { margin-top: .6rem; }
.stack p { margin: 0 0 .6rem; }
.row { display: flex; gap: 1rem; flex-wrap: wrap; align-items: end; }
.row label { flex: 1; min-width: 180px; }

label { display: block; font-weight: 600; font-size: .85rem; color: #3b3f45; }
input[type=text], input[type=password], input[type=number], input:not([type]), select, textarea {
  display: block; width: 100%; margin-top: .25rem; padding: .5rem .65rem; font: inherit; font-weight: 400; color: var(--ink);
  background: #fff; border: 1px solid #d5d0c5; border-radius: 7px;
}
input[type=checkbox] { width: auto; display: inline; margin-right: .35rem; }
.check { font-weight: 400; }
input:focus, select:focus, textarea:focus { outline: 2px solid var(--accent-soft); border-color: var(--accent); }
textarea { resize: vertical; font-family: var(--sans); }
.helptext { display: block; color: var(--muted); font-weight: 400; font-size: .8rem; margin-top: .2rem; }
.errorlist { color: var(--again); margin: .25rem 0; padding-left: 1rem; font-size: .85rem; }

.btn { display: inline-flex; align-items: center; justify-content: center; gap: .3rem; padding: .5rem .95rem; border: 1px solid #d0cbc0; border-radius: 8px; background: var(--surface); color: var(--ink); font: inherit; font-weight: 600; cursor: pointer; text-decoration: none; }
.btn:hover { background: #f1eee7; text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.primary:hover { background: #1b4d59; }
.btn.danger { color: var(--again); border-color: #e9c3bf; }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn.wide { width: 100%; padding: .85rem; font-size: 1rem; }
.linkish { background: none; border: 0; color: var(--accent); cursor: pointer; font: inherit; padding: 0; }

.flash { padding: .65rem .9rem; border-radius: 8px; margin-bottom: 1rem; border: 1px solid; }
.flash-success { background: #ecf7ef; border-color: #b9e0c3; color: #14532d; }
.flash-error { background: #fdf0ee; border-color: #f2c4bd; color: #8a1c12; }
.flash-warning { background: #fff7e6; border-color: #f1d9a0; color: #7a4d00; }
.flash-info { background: var(--accent-soft); border-color: #bcd8dd; color: #173f48; }

table { border-collapse: collapse; width: 100%; }
th { text-align: left; font-size: .75rem; text-transform: uppercase; letter-spacing: .04em; color: var(--muted); font-weight: 600; }
th, td { padding: .55rem .6rem; border-bottom: 1px solid var(--line); vertical-align: top; }
.num { text-align: right; font-variant-numeric: tabular-nums; }
.grid { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; }
.grid tbody tr:hover { background: #faf8f4; }
.grid tr.suspended td { background: #fbf6e4; color: var(--muted); }
.narrow-table { max-width: 560px; }
.kv th { text-transform: none; font-size: .9rem; color: var(--ink); font-weight: 500; letter-spacing: 0; }

.decks { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.decks td { vertical-align: middle; padding: .7rem .8rem; }
.indent { display: inline-block; width: calc(var(--depth) * 1.4rem); }
.deck-name { font-weight: 600; font-size: 1rem; color: var(--ink); }
.c-new { color: var(--new); font-weight: 600; }
.c-learn { color: var(--learn); font-weight: 600; }
.c-due { color: var(--due); font-weight: 600; }
td.c-new, td.c-learn, td.c-due { font-variant-numeric: tabular-nums; }
.row-actions { text-align: right; }
.pill { display: inline-block; font-size: .72rem; padding: .05rem .5rem; border-radius: 99px; background: var(--accent-soft); color: var(--accent); margin-left: .4rem; font-weight: 600; vertical-align: middle; }
.empty { text-align: center; padding: 2.5rem; }

.tabs { display: flex; gap: .25rem; margin-bottom: 1rem; border-bottom: 1px solid var(--line); }
.tabs a { padding: .5rem .9rem; color: var(--muted); border-bottom: 2px solid transparent; margin-bottom: -1px; }
.tabs a.active { color: var(--accent); border-color: var(--accent); font-weight: 600; }

.searchbar { display: flex; gap: .5rem; }
.searchbar input { margin: 0; font-family: var(--mono); }
.chip { display: inline-block; font-family: var(--mono); font-size: .8rem; background: var(--surface); border: 1px solid var(--line); border-radius: 6px; padding: .05rem .45rem; margin: .15rem .15rem; color: var(--ink); }
.toolbar { display: flex; gap: .6rem; align-items: center; margin: .75rem 0; }
.toolbar select { width: auto; margin: 0; }
.toolbar span { flex: 1; color: var(--muted); }
.tag { display: inline-block; font-size: .75rem; background: #f0ede6; border-radius: 5px; padding: 0 .4rem; margin: 0 .2rem .2rem 0; }
.st { font-size: .78rem; font-weight: 600; padding: .05rem .45rem; border-radius: 5px; }
.st-0 { background: #e8effd; color: var(--new); }
.st-1, .st-3 { background: #fdeee5; color: var(--learn); }
.st-2 { background: #e7f5ec; color: var(--due); }

/* study */
.studying .page { max-width: 760px; }
.study-head { display: flex; align-items: center; gap: .75rem; margin-bottom: .75rem; }
.study-head .counts { margin-left: auto; font-size: 1.05rem; font-variant-numeric: tabular-nums; }
.cardface { background: var(--surface); border: 1px solid var(--line); border-radius: 14px; box-shadow: var(--shadow); min-height: 300px; padding: 2.5rem 2rem; font-family: var(--serif); }
.card { font-size: 1.6rem; text-align: center; line-height: 1.45; overflow-wrap: anywhere; }
.card hr, .card hr#answer { border: 0; border-top: 1px solid var(--line); margin: 1.4rem 0; }
.cloze { font-weight: 700; color: var(--accent); }
.typeans { font-family: var(--mono); font-size: 1.1rem; text-align: center; max-width: 420px; margin: 1.2rem auto 0; }
.typed { font-family: var(--mono); font-size: 1.15rem; margin-top: .6rem; }
.typed .ok { background: #dcf3e2; color: #14532d; }
.typed .bad { background: #fbe0dc; color: #8a1c12; text-decoration: line-through; }
.typed .miss { background: #fff1c7; color: #6b4a00; }
.typed .arrow { color: var(--muted); }
.answerbar { margin-top: 1rem; }
.grades { display: grid; grid-template-columns: repeat(4, 1fr); gap: .5rem; }
.grade { border: 1px solid var(--line); border-radius: 10px; background: var(--surface); padding: .65rem .3rem; font: inherit; font-weight: 600; cursor: pointer; display: flex; flex-direction: column; align-items: center; gap: .1rem; }
.grade .ivl { font-size: .78rem; font-weight: 500; color: var(--muted); }
.grade:hover { transform: translateY(-1px); box-shadow: var(--shadow); }
.g1 { color: var(--again); } .g2 { color: var(--hard); } .g3 { color: var(--good); } .g4 { color: var(--easy); }
.study-foot { text-align: center; font-size: .85rem; margin-top: 1rem; }
.done { text-align: center; padding: 2.5rem; }
.hint summary { cursor: pointer; color: var(--accent); font-size: 1rem; }

/* editor */
.editor { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 1.25rem; align-items: start; }
.preview h2 { color: var(--muted); font-size: .8rem; text-transform: uppercase; letter-spacing: .05em; }
.preview-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: .9rem 1rem; margin-bottom: .9rem; box-shadow: var(--shadow); }
.preview-card h3 { margin: 0 0 .5rem; font-size: .85rem; color: var(--muted); }
.preview-card .side { border-top: 1px dashed var(--line); padding: .6rem 0; font-family: var(--serif); }
.preview-card .card { font-size: 1.15rem; }
.side-label { font: 600 .7rem var(--sans); text-transform: uppercase; color: var(--muted); letter-spacing: .05em; }

/* stats */
.tiles { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: .75rem; margin: 1rem 0; }
.tile { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: .9rem 1rem; box-shadow: var(--shadow); }
.tile b { display: block; font-size: 1.35rem; font-variant-numeric: tabular-nums; }
.tile span { color: var(--muted); font-size: .82rem; }
svg.bars, svg.heatmap { width: 100%; height: auto; display: block; }
svg .bar { fill: var(--accent); opacity: .85; }
svg .bar:hover { opacity: 1; }
svg .bar-label { font: 9px var(--sans); fill: var(--muted); text-anchor: middle; }
svg .bar-value { font: 9px var(--sans); fill: var(--ink); text-anchor: middle; }
svg .hm-label { font: 8px var(--sans); fill: var(--muted); }
.hm0 { fill: #ebe7de; } .hm1 { fill: #b7d6dc; } .hm2 { fill: #74aeb9; } .hm3 { fill: #3a8494; } .hm4 { fill: #1b5562; }
.samples div { font-size: .85rem; color: var(--muted); }

.auth { max-width: 400px; margin: 3rem auto; background: var(--surface); padding: 2rem; border-radius: 14px; border: 1px solid var(--line); box-shadow: var(--shadow); }

@media (max-width: 760px) {
  .topbar { flex-wrap: wrap; gap: .5rem; padding: .6rem 1rem; }
  .page { padding: 1rem; }
  .editor { grid-template-columns: 1fr; }
  .cardface { padding: 1.5rem 1rem; }
  .grid { display: block; overflow-x: auto; }
}