:root {
  --bg: #1e232b;
  --panel: #262c37;
  --panel-2: #2d3442;
  --text: #e8ecf3;
  --muted: #98a2b3;
  --accent: #4f8cff;
  --accent-strong: #3b74e8;
  --danger: #e5484d;
  --good: #46a758;
  --dark-sq: #779556;
  --light-sq: #ebecd0;
  --dark-sq-move: #baca2b;
  --light-sq-move: #f5f682;
  --border: rgba(255, 255, 255, 0.08);
  --shadow: 0 12px 40px rgba(0, 0, 0, 0.4);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
}

body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 15px;
  line-height: 1.45;
  display: flex;
  justify-content: center;
  padding: 20px 16px 28px;
}

.app {
  width: 100%;
  max-width: 1080px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

/* ------------------------------------------------------------------ header */

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.app-header h1 {
  margin: 0;
  font-size: 22px;
  font-weight: 650;
  letter-spacing: 0.02em;
}

.header-controls {
  display: flex;
  gap: 10px;
  align-items: flex-end;
  flex-wrap: wrap;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.field-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

/* A checkbox reads as a row rather than a stacked label over a control, and
   sits on the baseline of the neighbouring selects. */
.field-check {
  flex-direction: row;
  align-items: center;
  gap: 7px;
  padding-bottom: 8px;
  cursor: pointer;
}

.field-check input {
  accent-color: var(--accent);
  width: 15px;
  height: 15px;
  margin: 0;
  cursor: pointer;
}

.field-check input:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

select, textarea {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 7px 10px;
  font-size: 14px;
  font-family: inherit;
}

select:focus, textarea:focus, .btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

/* ------------------------------------------------------------------ layout */

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 20px;
  align-items: start;
}

@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }
  body { padding: 12px 10px 24px; }
}

.board-area {
  display: flex;
  flex-direction: column;
  gap: 8px;
  min-width: 0;
}

.board-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 1;
}

/* ------------------------------------------------------------------ board */

.board {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
  border-radius: 4px;
  overflow: hidden;
  box-shadow: var(--shadow);
  background: var(--dark-sq);
  user-select: none;
  -webkit-user-select: none;
}

.square {
  position: relative;
  border: 0;
  padding: 0;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.square.dark { background: var(--dark-sq); }
.square.light { background: var(--light-sq); }

.square.from { box-shadow: inset 0 0 0 3px var(--accent-strong); }
.square.checked { box-shadow: inset 0 0 0 3px var(--danger); }
.square.last-move.dark { background: var(--dark-sq-move); }
.square.last-move.light { background: var(--light-sq-move); }

.square.dark.selectable { background: color-mix(in srgb, var(--dark-sq) 82%, var(--accent)); }
.square.light.selectable { background: color-mix(in srgb, var(--light-sq) 78%, var(--accent)); }

.square .coord {
  position: absolute;
  font-size: clamp(8px, 1.3vmin, 11px);
  font-weight: 600;
  color: rgba(0, 0, 0, 0.55);
  pointer-events: none;
}

.square .coord.file { bottom: 2px; right: 4px; }
.square .coord.rank { top: 2px; left: 4px; }
.square.dark .coord { color: rgba(255, 255, 255, 0.5); }

/* Pieces live in a slot so the square can be re-skinned without touching them. */
.piece-slot {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 1;
}

/* The piece being taken, left behind to fade while its captor arrives. It sits
   under the slot so the arriving piece is the one on top. */
.capture-ghost {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
}

.capture-ghost svg { width: 100%; height: 100%; }

.piece {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

/* The piece left behind on the square while its copy follows the pointer. */
.piece-slot.ghost {
  opacity: 0.3;
}

/* Move hints: a dot for quiet moves, a ring for captures. */
.hint::after {
  content: "";
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

.hint.quiet::after {
  width: 100%;
  height: 100%;
  background: radial-gradient(circle, rgba(0,0,0,0.22) 0 18%, transparent 18%);
}

.hint.capture::after {
  background: radial-gradient(circle, transparent 0 52%, rgba(0,0,0,0.22) 53% 67%, transparent 68%);
}

/* The piece that is being dragged. Centred on the pointer. */
#dragged {
  position: fixed;
  z-index: 50;
  width: var(--drag-size, 64px);
  height: var(--drag-size, 64px);
  transform: translate(-50%, -50%);
  pointer-events: none;
  will-change: left, top;
}

#dragged svg { width: 100%; height: 100%; }

/* While the engine thinks, the board is inert — say so with the cursor. */
.board.busy { cursor: progress; }
.board.busy .square { cursor: progress; }

/* ------------------------------------------------------------------ overlays */

.promotion-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(12, 15, 20, 0.55);
  border-radius: 4px;
  /* `isolation` keeps a piece lifted mid-slide from rising above the dialog. */
  z-index: 30;
  isolation: isolate;
}

/* An author `display` rule outranks the UA stylesheet's `[hidden] { display: none }`,
   so elements toggled via the hidden attribute need it restored explicitly. */
[hidden] { display: none !important; }

.promotion-dialog {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px;
  box-shadow: var(--shadow);
  text-align: center;
  min-width: 240px;
}

.promotion-dialog h2 {
  margin: 0 0 12px;
  font-size: 16px;
  font-weight: 600;
}

.promotion-choices {
  display: grid;
  grid-template-columns: repeat(4, 56px);
  gap: 8px;
  justify-content: center;
}

.promo-btn {
  border: 0;
  border-radius: 8px;
  padding: 6px;
  background: var(--panel-2);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  aspect-ratio: 1;
  transition: background 0.12s;
}

.promo-btn:hover, .promo-btn:focus-visible {
  background: var(--accent);
  outline: none;
}

.promo-btn svg { width: 100%; height: 100%; }

.result-banner {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
  box-shadow: var(--shadow);
}

.result-banner .result-text {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 0;
  flex: 1 1 auto;
}

.result-banner #result-title { font-size: 15px; font-weight: 600; }
.result-banner #result-detail { color: var(--muted); font-size: 13px; }

.result-close {
  border: 0;
  background: transparent;
  color: var(--muted);
  font-size: 20px;
  line-height: 1;
  padding: 4px 8px;
  border-radius: 6px;
  cursor: pointer;
}

.result-close:hover, .result-close:focus-visible {
  color: var(--text);
  background: var(--panel-2);
  outline: none;
}

/* ------------------------------------------------------------------ players */

.player-strip {
  display: flex;
  align-items: center;
  gap: 10px;
  min-height: 26px;
  font-size: 14px;
}

.player-strip .player-name { font-weight: 600; }

.player-strip.active .player-name {
  color: var(--accent);
}

.captured {
  display: flex;
  flex-wrap: wrap;
  gap: 1px;
  min-height: 18px;
}

.captured svg { width: 18px; height: 18px; }
.captured svg.dim { opacity: 0.45; }
.captured svg.captured-piece { width: 16px; height: 16px; opacity: 0.55; }

.material {
  margin-left: auto;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

/* ------------------------------------------------------------------ panel */

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-width: 0;
}

.status { font-size: 14px; }

.status-turn { font-weight: 650; }

.status-detail { color: var(--muted); font-size: 13px; display: block; margin-top: 2px; }

.eval-row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.eval-bar {
  flex: 1;
  height: 10px;
  border-radius: 5px;
  background: #11141a;
  overflow: hidden;
  border: 1px solid var(--border);
}

.eval-fill {
  height: 100%;
  width: 50%;
  background: var(--text);
  transition: width 0.25s ease, background 0.25s ease;
}

.eval-text {
  min-width: 64px;
  text-align: right;
  font-size: 12px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.moves-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  font-size: 13px;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
  padding-bottom: 6px;
}

.thinking {
  color: var(--accent);
  animation: pulse 1.2s ease-in-out infinite;
}

@keyframes pulse { 50% { opacity: 0.35; } }

.moves {
  margin: 0;
  padding: 0;
  list-style: none;
  height: 232px;
  overflow-y: auto;
  display: grid;
  grid-template-columns: 34px 1fr 1fr;
  align-items: baseline;
  gap: 2px 6px;
  font-size: 14px;
  font-variant-numeric: tabular-nums;
  scrollbar-width: thin;
}

.moves li { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.moves li.no { color: var(--muted); font-size: 12px; text-align: right; }
.moves li.move { padding: 1px 4px; border-radius: 4px; cursor: pointer; }
.moves li.move:hover { background: var(--panel-2); }
.moves li.current { background: var(--accent); color: white; }

.controls {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.btn {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 12px;
  font-size: 14px;
  font-family: inherit;
  cursor: pointer;
  transition: background 0.12s, transform 0.05s;
}

.btn:hover { background: #374052; }
.btn:active { transform: translateY(1px); }

.btn-primary {
  background: var(--accent-strong);
  border-color: transparent;
  font-weight: 600;
}

.btn-primary:hover { background: var(--accent-strong); filter: brightness(1.1); }

.btn-small { padding: 5px 9px; font-size: 12px; }

.fen-box summary {
  cursor: pointer;
  font-size: 13px;
  color: var(--muted);
}

.fen-box textarea {
  width: 100%;
  margin-top: 8px;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  font-size: 12px;
  resize: vertical;
}

.fen-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
}

.fen-msg { font-size: 12px; color: var(--muted); }
.fen-msg.error { color: var(--danger); }
.fen-msg.ok { color: var(--good); }

@media (max-width: 860px) {
  .moves { height: 168px; }
}

/* ------------------------------------------------------------------ loading
 * Full-screen card while the neural net's weights are downloading. */

.loading-overlay {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(12, 15, 20, 0.72);
  backdrop-filter: blur(3px);
  padding: 20px;
}

.loading-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 26px 28px;
  box-shadow: var(--shadow);
  text-align: center;
  width: 100%;
  max-width: 360px;
}

.loading-card h2 {
  margin: 14px 0 6px;
  font-size: 17px;
  font-weight: 650;
}

.loading-card p {
  margin: 0 0 16px;
  color: var(--muted);
  font-size: 13.5px;
  overflow-wrap: anywhere;
}

.loading-spinner {
  width: 38px;
  height: 38px;
  margin: 0 auto;
  border-radius: 50%;
  border: 3px solid var(--panel-2);
  border-top-color: var(--accent);
  animation: spin 0.9s linear infinite;
}

@keyframes spin { to { transform: rotate(360deg); } }

.loading-bar {
  height: 8px;
  border-radius: 4px;
  background: #11141a;
  overflow: hidden;
  border: 1px solid var(--border);
}

.loading-fill {
  height: 100%;
  width: 0%;
  background: var(--accent);
  transition: width 0.2s ease;
}

#loading-retry { margin-top: 16px; }

/* ------------------------------------------------------------------ mobile */

html { -webkit-text-size-adjust: 100%; }

@media (max-width: 560px) {
  body {
    padding: 10px 8px 20px;
    padding-bottom: max(20px, env(safe-area-inset-bottom));
  }

  .app { gap: 10px; }

  .app-header { gap: 10px; }
  .app-header h1 { font-size: 18px; }

  /* Controls become a 2x2 grid; the checkbox spans the full row. */
  .header-controls {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 8px;
    width: 100%;
    align-items: end;
  }
  .header-controls .field-check {
    grid-column: 1 / -1;
    padding-bottom: 0;
  }

  /* 16px inputs stop iOS Safari from zooming in on focus. */
  select, textarea { font-size: 16px; width: 100%; }

  .panel { padding: 12px; }
  .moves { height: 150px; font-size: 15px; }
  .eval-text { min-width: 56px; }

  .controls { gap: 10px; }
  .btn { min-height: 44px; padding: 10px 12px; }

  .promotion-dialog { min-width: 0; width: 86vw; }

  .square, .btn, select, textarea { touch-action: manipulation; }
}

/* Landscape phones: keep the board on screen instead of filling the width. */
@media (max-height: 520px) and (orientation: landscape) {
  .board-wrap {
    width: min(100%, calc(100vh - 170px));
    align-self: center;
  }
  .moves { height: 120px; }
}