:root {
  --paper: #eef3f1;
  --grid: #d9e4e0;
  --sheet: #fbfcfb;
  --ink: #1c2a44;
  --ink-2: #56627a;
  --rule: #c7d4cf;
  --hl: #f6e35c;
  --hl-ink: #1c2a44;
  --red: #b8362a;
  --red-soft: #f6e1dd;
  --green: #256f4f;
  --green-soft: #dcefe5;
  --focus: #2f64d6;
  --serif: "Spectral", Georgia, "Times New Roman", serif;
  --sans: "Public Sans", "Segoe UI", system-ui, sans-serif;
  --cell: 24px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #102038;
    --grid: #1b3050;
    --sheet: #152945;
    --ink: #e3ebf6;
    --ink-2: #9fb1ca;
    --rule: #2c4568;
    --hl: #e9d64b;
    --hl-ink: #102038;
    --red: #ff8a7a;
    --red-soft: #3a2432;
    --green: #6fd3a3;
    --green-soft: #173a36;
    --focus: #8fb4ff;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font: 400 1rem/1.55 var(--sans);
  color: var(--ink);
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: var(--cell) var(--cell);
}

a { color: inherit; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

/* Masthead */
.masthead {
  display: flex;
  align-items: baseline;
  gap: 1.5rem;
  flex-wrap: wrap;
  padding: 1rem 16px;
  max-width: 820px;
  margin: 0 auto;
}
.wordmark {
  font: 700 1.6rem/1 var(--serif);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.masthead nav { display: flex; gap: 1.1rem; }
.masthead nav a {
  text-decoration: none;
  color: var(--ink-2);
  font-weight: 500;
  padding-bottom: 2px;
  border-bottom: 2px solid transparent;
}
.masthead nav a[aria-current="page"] { color: var(--ink); border-bottom-color: var(--ink); }
.spend { margin-left: auto; color: var(--ink-2); font-size: 0.875rem; }

main {
  max-width: 820px;
  margin: 0 auto 4rem;
  padding: 0 16px;
}
main:focus { outline: none; }

/* The sheet: a piece of paper lying on the grid */
.sheet {
  background: var(--sheet);
  border: 1px solid var(--rule);
  box-shadow: 5px 5px 0 var(--grid);
  padding: 1.75rem clamp(1rem, 4vw, 2.5rem) 2rem;
}

h1, h2, h3 { font-family: var(--serif); line-height: 1.2; margin: 0; }
h1 { font-size: clamp(1.9rem, 4vw, 2.5rem); font-weight: 600; letter-spacing: -0.01em; }
h2 { font-size: 1.35rem; font-weight: 600; margin-top: 2.25rem; margin-bottom: 0.75rem; }
h3 { font-size: 1.1rem; font-weight: 600; margin: 1.5rem 0 0.5rem; }
.lede { color: var(--ink-2); max-width: 62ch; margin: 0.6rem 0 1.5rem; }
.muted { color: var(--ink-2); }
.small { font-size: 0.875rem; }

/* Controls */
.button {
  font: 600 0.95rem/1 var(--sans);
  padding: 0.75rem 1.1rem;
  border-radius: 6px;
  border: 1.5px solid var(--ink);
  background: var(--sheet);
  color: var(--ink);
  cursor: pointer;
}
.button.primary { background: var(--ink); color: var(--sheet); }
.button.quiet { border-color: var(--rule); }
.button:disabled { opacity: 0.55; cursor: progress; }
.linklike {
  background: none; border: 0; padding: 0; color: var(--ink-2);
  font: inherit; text-decoration: underline; text-underline-offset: 3px; cursor: pointer;
}

.filters { display: flex; flex-wrap: wrap; gap: 0.75rem 1.25rem; margin-bottom: 1.25rem; }
label.field { display: flex; flex-direction: column; gap: 0.3rem; font-size: 0.875rem; font-weight: 600; }
select, input[type="text"], input[type="number"] {
  font: 400 1rem/1.3 var(--sans);
  color: var(--ink);
  background: var(--sheet);
  border: 1.5px solid var(--rule);
  border-radius: 6px;
  padding: 0.55rem 0.7rem;
  min-width: 10rem;
}
input[type="number"] { min-width: 6rem; width: 6rem; }

/* Rows (puzzle and graveyard lists) */
.rows { list-style: none; margin: 0; padding: 0; border-top: 1px solid var(--rule); }
.rows li { border-bottom: 1px solid var(--rule); }
.row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.25rem 1rem;
  padding: 0.95rem 0.25rem;
  text-decoration: none;
}
.row:hover .row-title { text-decoration: underline; text-underline-offset: 4px; }
.row-title { font: 500 1.2rem/1.3 var(--serif); }
.row-meta { grid-column: 1; display: flex; flex-wrap: wrap; gap: 0.35rem 1rem; color: var(--ink-2); font-size: 0.875rem; }
.row-side { grid-column: 2; grid-row: 1 / span 2; align-self: center; font-size: 0.875rem; font-weight: 600; }
.row-side.correct { color: var(--green); }
.row-side.wrong { color: var(--red); }

/* Difficulty: filled graph-paper cells */
.difficulty { display: inline-flex; align-items: center; gap: 0.4rem; }
.cells { display: inline-flex; gap: 2px; }
.cells i { width: 9px; height: 9px; border: 1.5px solid currentColor; display: block; }
.cells i.on { background: currentColor; }

.empty { padding: 2rem 0 0.5rem; }
.empty p { margin: 0 0 1rem; max-width: 52ch; }

/* Puzzle page */
.back { display: inline-block; margin-bottom: 1rem; color: var(--ink-2); font-size: 0.9rem; }
.meta-line { display: flex; flex-wrap: wrap; gap: 0.5rem 1.25rem; color: var(--ink-2); font-size: 0.9rem; margin: 0.6rem 0 1.5rem; }
.illustration { margin: 0 0 1.5rem; border: 1px solid var(--rule); background: #fbf8f1; }
.illustration img { display: block; width: 100%; height: auto; }
.statement { font: 400 1.2rem/1.65 var(--serif); max-width: 66ch; }
.statement p { margin: 0 0 0.9em; }
.precise {
  margin-top: 1rem;
  padding: 0.9rem 1rem;
  border-left: 3px solid var(--rule);
  font: 400 1rem/1.6 var(--serif);
  color: var(--ink-2);
}
.precise p { margin: 0 0 0.6em; }

/* Hint ladder: the one bold element */
.ladder { list-style: none; margin: 0; padding: 0 0 0 0.25rem; position: relative; }
.ladder::before {
  content: ""; position: absolute; left: calc(0.25rem + 15px); top: 16px; bottom: 16px;
  border-left: 2px dashed var(--rule);
}
.rung { position: relative; display: grid; grid-template-columns: 32px 1fr; gap: 0 1rem; padding: 0.35rem 0; }
.rung-num {
  width: 32px; height: 32px; border-radius: 50%;
  display: grid; place-items: center;
  font: 700 0.95rem/1 var(--sans);
  background: var(--sheet); border: 2px solid var(--rule); color: var(--ink-2);
  position: relative; z-index: 1;
}
.rung.revealed .rung-num { background: var(--hl); border-color: var(--hl); color: var(--hl-ink); }
.rung-body { align-self: center; min-height: 32px; display: flex; align-items: center; }
.rung.revealed .rung-body { display: block; font: 400 1.05rem/1.6 var(--serif); padding-top: 0.2rem; }
.rung.revealed .rung-body p { margin: 0 0 0.5em; }
.rung.locked .rung-body { color: var(--ink-2); font-size: 0.9rem; }
.rung.just-revealed .rung-body { animation: unfold 260ms ease-out; }
@keyframes unfold { from { opacity: 0; transform: translateY(-4px); } to { opacity: 1; transform: none; } }

/* Answer */
.answer-form { display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: flex-end; }
.answer-form input { font-size: 1.1rem; min-width: 12rem; }
.hint-text { flex-basis: 100%; margin: 0; color: var(--ink-2); font-size: 0.875rem; }
.form-error { flex-basis: 100%; margin: 0; color: var(--red); font-weight: 600; font-size: 0.9rem; }

.verdict { padding: 1.1rem 1.25rem; border-radius: 6px; margin-bottom: 1.25rem; }
.verdict.correct { background: var(--green-soft); }
.verdict.wrong { background: var(--red-soft); }
.verdict-title { font: 600 1.5rem/1.2 var(--serif); margin: 0 0 0.35rem; }
.verdict.correct .verdict-title { color: var(--green); }
.verdict.wrong .verdict-title { color: var(--red); }
.verdict p { margin: 0.2rem 0; }
.key { font: 700 1.25rem var(--serif); background: linear-gradient(transparent 55%, var(--hl) 55%); color: var(--ink); padding: 0 0.15em; }

.solution { font: 400 1.05rem/1.65 var(--serif); max-width: 68ch; }
.solution p { margin: 0 0 0.9em; }
.solution .katex-display { overflow-x: auto; overflow-y: hidden; padding: 0.25rem 0; }

details { margin-top: 1.25rem; border-top: 1px solid var(--rule); padding-top: 0.75rem; }
summary { cursor: pointer; font-weight: 600; }
pre {
  background: var(--paper);
  border: 1px solid var(--rule);
  padding: 0.9rem 1rem;
  overflow-x: auto;
  font: 0.85rem/1.5 ui-monospace, "Cascadia Code", Consolas, monospace;
  max-height: 28rem;
}

/* Graveyard: proofreader's red pencil */
.reason {
  font: italic 500 1rem/1.3 var(--serif);
  color: var(--red);
  padding-left: 0.6rem;
  border-left: 3px solid var(--red);
}
.graveyard .row-title { text-decoration: line-through; text-decoration-color: color-mix(in srgb, var(--red) 55%, transparent); text-decoration-thickness: 1.5px; }
.graveyard .row:hover .row-title { text-decoration: line-through underline; }
.rejection { border-left: 3px solid var(--red); padding: 0.4rem 0 0.4rem 1rem; margin: 0 0 1.5rem; }
.rejection .reason { border: 0; padding: 0; font-size: 1.3rem; }
.rejection p { margin: 0.4rem 0 0; }
.compare { display: grid; grid-template-columns: repeat(auto-fit, minmax(12rem, 1fr)); gap: 1rem; margin: 0 0 1rem; }
.compare div { border: 1px solid var(--rule); padding: 0.75rem 1rem; }
.compare dt { font-size: 0.85rem; color: var(--ink-2); }
.compare dd { margin: 0.2rem 0 0; font: 600 1.3rem var(--serif); }

/* Generate */
.chips { display: flex; flex-wrap: wrap; gap: 0.5rem; border: 0; padding: 0; margin: 0 0 1.25rem; }
.chips legend { font-size: 0.875rem; font-weight: 600; margin-bottom: 0.4rem; padding: 0; }
.chip input { position: absolute; opacity: 0; pointer-events: none; }
.chip span {
  display: inline-block; padding: 0.4rem 0.8rem; border-radius: 999px;
  border: 1.5px solid var(--rule); cursor: pointer; font-size: 0.9rem; background: var(--sheet);
}
.chip input:checked + span { background: var(--ink); border-color: var(--ink); color: var(--sheet); }
.chip input:focus-visible + span { outline: 2px solid var(--focus); outline-offset: 2px; }
.form-row { display: flex; flex-wrap: wrap; gap: 1rem 1.5rem; align-items: flex-end; margin-bottom: 1.5rem; }

.batch { border-top: 1px solid var(--rule); padding-top: 1rem; margin-top: 1rem; }
.batch-head { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 0.5rem; font-weight: 600; margin-bottom: 0.5rem; }
.job { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 0.2rem 1rem; padding: 0.6rem 0; border-bottom: 1px dashed var(--rule); }
.job-title { font: 500 1.05rem/1.3 var(--serif); }
.job-meta { color: var(--ink-2); font-size: 0.85rem; }
.track { display: flex; gap: 3px; align-items: center; grid-column: 2; grid-row: 1 / span 2; }
.track i { width: 26px; height: 8px; border: 1.5px solid var(--ink-2); display: block; }
.track i.on { background: var(--ink-2); }
.track i.now { background: var(--hl); border-color: var(--ink); animation: pulse 1.2s ease-in-out infinite; }
@keyframes pulse { 50% { opacity: 0.45; } }
.outcome-valid { color: var(--green); font-weight: 600; }
.outcome-grave { color: var(--red); font-weight: 600; }

.notice { padding: 0.9rem 1rem; border-left: 3px solid var(--red); background: var(--red-soft); margin: 1rem 0; }

dialog {
  border: 1px solid var(--rule); background: var(--sheet); color: var(--ink);
  padding: 1.5rem; max-width: min(28rem, calc(100vw - 32px)); box-shadow: 6px 6px 0 var(--grid);
}
dialog::backdrop { background: rgb(16 32 56 / 0.45); }
dialog h2 { margin: 0 0 0.5rem; }
.dialog-actions { display: flex; justify-content: flex-end; gap: 0.75rem; margin-top: 1.25rem; }

@media (max-width: 560px) {
  .spend { margin-left: 0; flex-basis: 100%; }
  .row { grid-template-columns: 1fr; }
  .row-side { grid-column: 1; grid-row: auto; }
  .job { grid-template-columns: 1fr; }
  .track { grid-column: 1; grid-row: auto; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}