/* Sudoku - dark theme.
   Black ground, matrix green for everything that matters: the grid frame, the
   primary action, solved digits, focus. Everything else stays quiet so the
   green reads as signal rather than decoration. */

:root {
  --bg: #050705;
  --bg-raised: #0a0e0a;
  --panel: #0c120c;
  --line: #1a241a;
  --line-strong: #2b3b2b;
  --text: #d9e6d9;
  --muted: #7f9a7f;
  --faint: #4c5f4c;

  --green: #00ff41;
  --green-dim: #00c837;
  --green-ink: #06210b;
  --green-glow: rgba(0, 255, 65, 0.35);
  --green-tint: rgba(0, 255, 65, 0.10);

  --red: #ff4d4d;
  --red-tint: rgba(255, 77, 77, 0.16);
  --amber: #ffb547;
  --amber-tint: rgba(255, 181, 71, 0.16);

  --cell: 48px;
  --radius: 10px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

html {
  background: var(--bg);
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.5;
  color: var(--text);
  background:
    radial-gradient(900px 500px at 50% -10%, rgba(0, 255, 65, 0.07), transparent 70%),
    var(--bg);
  -webkit-font-smoothing: antialiased;
}

/* ---- Header ------------------------------------------------------------ */

.topbar {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 18px;
  padding: 22px clamp(16px, 4vw, 40px) 18px;
  border-bottom: 1px solid var(--line);
  background: rgba(5, 7, 5, 0.7);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

.brand .mark {
  display: inline-flex;
  color: var(--green);
  filter: drop-shadow(0 0 6px var(--green-glow));
}

.brand h1 {
  margin: 0;
  font-size: 20px;
  font-weight: 650;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.tagline {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

/* ---- Layout ------------------------------------------------------------ */

main {
  flex: 1;
  width: 100%;
  max-width: 1240px;
  margin: 0 auto;
  padding: 24px clamp(16px, 4vw, 40px) 40px;
}

.foot {
  padding: 16px clamp(16px, 4vw, 40px);
  border-top: 1px solid var(--line);
  color: var(--faint);
  font-size: 12px;
  text-align: center;
}

/* ---- Buttons ------------------------------------------------------------ */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 16px;
  font: inherit;
  font-weight: 500;
  color: var(--text);
  background: var(--bg-raised);
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  cursor: pointer;
  transition: border-color 120ms ease, background 120ms ease, color 120ms ease, box-shadow 120ms ease;
}

.btn:hover {
  border-color: var(--green-dim);
  color: #fff;
}

.btn:focus-visible {
  outline: none;
  border-color: var(--green);
  box-shadow: 0 0 0 3px var(--green-tint);
}

.btn:active {
  transform: translateY(1px);
}

.btn-quiet {
  color: var(--muted);
  background: transparent;
  border-color: transparent;
}

.btn-quiet:hover {
  color: var(--text);
  border-color: var(--line-strong);
}

.btn-icon {
  position: relative;
  padding: 6px;
  color: var(--muted);
  background: transparent;
  border-color: transparent;
  border-radius: 6px;
}

.btn-icon:hover {
  color: var(--green);
  background: var(--green-tint);
  border-color: transparent;
}

.btn-icon .icon-check {
  display: none;
}

.btn-icon.copied {
  color: var(--green);
}

.btn-icon.copied .icon-copy {
  display: none;
}

.btn-icon.copied .icon-check {
  display: block;
}

/* A word next to the icon while the copy is fresh, so the tick is not a puzzle. */
.btn-icon.copied::after {
  content: "Copied";
  position: absolute;
  right: calc(100% + 6px);
  top: 50%;
  transform: translateY(-50%);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--green);
  white-space: nowrap;
  pointer-events: none;
}

.btn-primary {
  gap: 10px;
  padding: 12px 22px;
  font-size: 16px;
  font-weight: 650;
  color: var(--green-ink);
  background: var(--green);
  border-color: var(--green);
  box-shadow: 0 0 18px var(--green-glow);
}

.btn-primary:hover {
  color: var(--green-ink);
  background: #33ff66;
  box-shadow: 0 0 26px var(--green-glow);
}

.btn-primary[disabled] {
  cursor: progress;
  opacity: 0.7;
}

/* ---- Toolbar and status ------------------------------------------------ */

.toolbar {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  margin-bottom: 22px;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
}

.status {
  margin: 0 auto;
  color: var(--muted);
  font-size: 14px;
  text-align: center;
  max-width: 62ch;
}

.alert {
  min-height: 1.5em;
  margin-top: 22px;
  font-family: var(--mono);
  font-size: 14px;
  letter-spacing: 0.02em;
}

.alert[data-kind="ok"] {
  color: var(--green);
  text-shadow: 0 0 10px var(--green-glow);
}

.alert[data-kind="error"] {
  color: var(--red);
}

.alert[data-kind="busy"] {
  color: var(--muted);
}

/* ---- Photo preview card ------------------------------------------------- */

.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.preview {
  margin: 0 auto 22px;
  width: fit-content;
  min-width: min(360px, 100%);
  max-width: 100%;
}

.preview-head {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  cursor: pointer;
  list-style: none;
  user-select: none;
  border-radius: var(--radius);
}

.preview-head::-webkit-details-marker {
  display: none;
}

.preview-head:hover {
  background: rgba(255, 255, 255, 0.03);
}

.preview-head:focus-visible {
  outline: none;
  box-shadow: inset 0 0 0 1px var(--green);
}

.preview-hint {
  flex: 1;
  color: var(--faint);
  font-size: 13px;
  text-align: right;
}

.preview-head .chevron {
  color: var(--muted);
  transition: transform 180ms ease;
}

.preview[open] .preview-head .chevron {
  transform: rotate(180deg);
}

.preview[open] .preview-head {
  border-bottom: 1px solid var(--line);
  border-bottom-left-radius: 0;
  border-bottom-right-radius: 0;
}

.preview-body {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 20px;
  padding: 16px;
}

.preview figure {
  margin: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.preview figcaption {
  color: var(--muted);
  font-size: 13px;
  text-align: center;
  max-width: 40ch;
}

#preview {
  display: block;
  width: 180px;
  height: 180px;
  border: 1px solid var(--line-strong);
  border-radius: 6px;
  background: #fff;
}

/* Corner picking: the fallback for a photo the detector cannot read. Four clicks
   from someone who can see the grid beats any amount of guessing. */
#picker {
  display: block;
  max-width: min(560px, 88vw);
  height: auto;
  border: 1px solid var(--line-strong);
  border-radius: 6px;
  cursor: crosshair;
}

/* ---- Boards ------------------------------------------------------------- */

.boards {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: flex-start;
  gap: 24px 28px;
}

.board-panel {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 10px;
}

.panel-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 30px;
  padding: 0 2px;
}

/* Solve sits under the puzzle and spans it, so the eye reads grid, then action. */
#solveBtn {
  width: 100%;
  justify-content: center;
  margin-top: 4px;
}

.panel-title {
  margin: 0;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
}

.board-frame {
  position: relative;
  padding: 8px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  transition: border-color 150ms ease, box-shadow 150ms ease;
}

.board {
  display: grid;
  grid-template-columns: repeat(9, var(--cell));
  grid-auto-rows: var(--cell);
  border: 2px solid var(--green);
  border-radius: 3px;
  box-shadow: 0 0 14px var(--green-glow), inset 0 0 14px rgba(0, 255, 65, 0.06);
  background: var(--bg);
}

.case {
  display: flex;
  align-items: center;
  justify-content: center;
  width: var(--cell);
  height: var(--cell);
  margin: 0;
  padding: 0;
  font-family: var(--mono);
  font-size: calc(var(--cell) * 0.46);
  font-weight: 500;
  font-variant-numeric: tabular-nums;
  text-align: center;
  color: var(--text);
  background: transparent;
  border: 0;
  border-right: 1px solid var(--line-strong);
  border-bottom: 1px solid var(--line-strong);
  transition: background 100ms ease;
}

/* Thick lines between the 3x3 boxes, the outer edge belongs to the frame. */
.case.x3 {
  border-right: 2px solid var(--green-dim);
}

.case.y3 {
  border-bottom: 2px solid var(--green-dim);
}

.board .case:nth-child(9n) {
  border-right: 0;
}

.board .case:nth-child(n + 73) {
  border-bottom: 0;
}

/* Inputs: the value is typed by the keyboard handler, the caret would only be noise. */
input.case {
  caret-color: transparent;
  outline: none;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
  border-radius: 0;
}

input.case::selection {
  background: transparent;
}

input.case:hover {
  background: rgba(255, 255, 255, 0.04);
}

.case.selected {
  background: var(--green-tint);
  box-shadow: inset 0 0 0 2px var(--green);
  color: #fff;
}

.case.conflict {
  background: var(--red-tint);
  color: var(--red);
}

.case.conflict.selected {
  box-shadow: inset 0 0 0 2px var(--red);
}

/* Amber, not red: the cell is not known to be wrong, only not trusted. Red is
   already spoken for by .conflict, which means a clue that breaks a rule. */
.case.uncertain {
  background: var(--amber-tint);
  color: var(--amber);
}

.case.uncertain.selected {
  box-shadow: inset 0 0 0 2px var(--amber);
}

.case.conflict.uncertain {
  background: var(--red-tint);
  color: var(--red);
}

/* Solution: the given clues stay as they were, the digits the solver found glow. */
.board.solved .case {
  color: var(--green);
  text-shadow: 0 0 8px var(--green-glow);
}

.board.solved .case.given {
  color: var(--text);
  text-shadow: none;
}

/* ---- Solution reveal ---------------------------------------------------- */

@keyframes reveal {
  from {
    opacity: 0;
    transform: translateX(-12px) scale(0.98);
  }

  to {
    opacity: 1;
    transform: none;
  }
}

#solutionPanel.reveal {
  animation: reveal 360ms cubic-bezier(0.2, 0.7, 0.2, 1) both;
}

@keyframes flash {
  from {
    box-shadow: 0 0 30px var(--green-glow), inset 0 0 40px rgba(0, 255, 65, 0.25);
  }

  to {
    box-shadow: 0 0 14px var(--green-glow), inset 0 0 14px rgba(0, 255, 65, 0.06);
  }
}

#solutionPanel.reveal .board {
  animation: flash 900ms ease-out 200ms both;
}

/* ---- Drag and drop ------------------------------------------------------ */

.drop-hint {
  position: absolute;
  inset: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 3px;
  background: rgba(5, 7, 5, 0.9);
  color: var(--green);
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-shadow: 0 0 10px var(--green-glow);
  opacity: 0;
  pointer-events: none;
  transition: opacity 150ms ease;
}

.drop-hint span {
  padding: 10px 18px;
  background: var(--bg);
  border: 1px dashed var(--green);
  border-radius: 6px;
}

body.dropping #problemFrame {
  border-color: var(--green);
  box-shadow: 0 0 0 1px var(--green), 0 0 32px var(--green-glow);
}

body.dropping #problemFrame .board {
  border-style: dashed;
}

body.dropping .drop-hint {
  opacity: 1;
}

/* ---- Small screens ------------------------------------------------------ */

@media (max-width: 640px) {
  :root {
    --cell: min(calc((100vw - 52px) / 9), 44px);
  }

  .boards {
    flex-direction: column;
    gap: 20px;
  }

  #solutionPanel.reveal {
    animation-name: reveal-up;
  }

  @keyframes reveal-up {
    from {
      opacity: 0;
      transform: translateY(12px);
    }

    to {
      opacity: 1;
      transform: none;
    }
  }
}

@media (prefers-reduced-motion: reduce) {

  #solutionPanel.reveal,
  #solutionPanel.reveal .board {
    animation: none;
  }
}