/* 網頁圖靈機 — ink & paper tape */
:root {
  --ink: #121a2b;
  --ink-2: #1a2740;
  --ink-3: #243352;
  --paper: #f3ead7;
  --paper-dim: #e4d8c0;
  --line: rgba(243, 234, 215, 0.14);
  --text: #eef2f8;
  --muted: #9aa8c0;
  --amber: #e6b422;
  --amber-glow: rgba(230, 180, 34, 0.45);
  --teal: #3dbeb6;
  --coral: #e07a5f;
  --sky: #7eb6ff;
  --radius: 12px;
  --font: "Noto Sans TC", "PingFang HK", "Microsoft JhengHei", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
  --shadow: 0 12px 40px rgba(0, 0, 0, 0.35);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  color-scheme: dark;
}

body {
  margin: 0;
  min-height: 100dvh;
  font-family: var(--font);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(62, 190, 182, 0.12), transparent 55%),
    radial-gradient(900px 500px at 100% 0%, rgba(230, 180, 34, 0.1), transparent 50%),
    var(--ink);
  color: var(--text);
  line-height: 1.55;
  -webkit-tap-highlight-color: transparent;
}

.app {
  width: min(1100px, 100%);
  margin: 0 auto;
  padding: 1rem 1rem calc(2rem + var(--safe-bottom));
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* —— Header —— */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.25rem 0.15rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.85rem;
}

.brand-mark {
  width: 2.4rem;
  height: 2.4rem;
  border-radius: 10px;
  background:
    linear-gradient(145deg, var(--amber) 0 28%, transparent 28% 36%, var(--paper) 36% 64%, transparent 64% 72%, var(--teal) 72%);
  box-shadow: 0 0 0 1px var(--line), var(--shadow);
  flex-shrink: 0;
}

.brand h1 {
  margin: 0;
  font-size: clamp(1.35rem, 4vw, 1.75rem);
  font-weight: 700;
  letter-spacing: 0.02em;
}

.tagline {
  margin: 0.15rem 0 0;
  color: var(--muted);
  font-size: 0.85rem;
}

.help {
  background: var(--ink-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.15rem;
}

.help h2 {
  margin: 0 0 0.5rem;
  font-size: 1rem;
}

.help ul {
  margin: 0;
  padding-left: 1.2rem;
  color: var(--muted);
}

.help li + li {
  margin-top: 0.4rem;
}

.help strong {
  color: var(--paper);
  font-weight: 600;
}

/* —— Buttons —— */
.btn {
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  border: 1px solid transparent;
  border-radius: 10px;
  padding: 0.55rem 1rem;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, transform 0.1s ease;
  touch-action: manipulation;
  min-height: 44px;
}

.btn:active {
  transform: scale(0.98);
}

.btn:focus-visible {
  outline: 2px solid var(--sky);
  outline-offset: 2px;
}

.btn-primary {
  background: var(--paper);
  color: var(--ink);
}

.btn-primary:hover {
  background: #fff6e6;
}

.btn-accent {
  background: var(--amber);
  color: #1a1400;
}

.btn-accent:hover {
  filter: brightness(1.05);
}

.btn-accent[data-mode="pause"] {
  background: var(--coral);
  color: #1a0a06;
}

.btn-secondary {
  background: var(--ink-3);
  color: var(--text);
  border-color: var(--line);
}

.btn-secondary:hover {
  background: #2c3d60;
}

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

.btn-ghost:hover {
  color: var(--text);
  border-color: rgba(243, 234, 215, 0.3);
}

.btn-icon {
  min-height: 36px;
  padding: 0.35rem 0.55rem;
  font-weight: 500;
}

/* —— Stage / tape —— */
.stage {
  background: var(--ink-2);
  border: 1px solid var(--line);
  border-radius: calc(var(--radius) + 2px);
  padding: 1rem;
  box-shadow: var(--shadow);
}

.stage-meta {
  margin-bottom: 0.85rem;
}

.tape-shell {
  position: relative;
  border-radius: 10px;
  background:
    repeating-linear-gradient(
      90deg,
      #2a1f12 0 2px,
      #3a2c18 2px 4px
    );
  padding: 0.65rem 0;
  overflow: hidden;
}

.tape-shell::before,
.tape-shell::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  width: 2.5rem;
  z-index: 2;
  pointer-events: none;
}

.tape-shell::before {
  left: 0;
  background: linear-gradient(90deg, rgba(18, 26, 43, 0.85), transparent);
}

.tape-shell::after {
  right: 0;
  background: linear-gradient(270deg, rgba(18, 26, 43, 0.85), transparent);
}

.tape-track {
  display: flex;
  gap: 0;
  overflow-x: auto;
  overflow-y: hidden;
  scroll-snap-type: x proximity;
  -webkit-overflow-scrolling: touch;
  padding: 0.35rem 2rem 0.5rem;
  scrollbar-width: thin;
  scrollbar-color: var(--amber) transparent;
}

.tape-cell {
  flex: 0 0 auto;
  width: 3.1rem;
  min-height: 4.2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  background: var(--paper);
  color: #1c1408;
  border-right: 1px solid #cbb894;
  scroll-snap-align: center;
  position: relative;
}

.tape-cell:first-child {
  border-radius: 6px 0 0 6px;
}

.tape-cell:last-child {
  border-radius: 0 6px 6px 0;
  border-right: none;
}

.tape-cell .sym {
  font-family: var(--mono);
  font-size: 1.35rem;
  font-weight: 600;
  line-height: 1;
}

.tape-cell .idx {
  font-family: var(--mono);
  font-size: 0.65rem;
  color: #7a6a4e;
}

.tape-cell.is-head {
  background: linear-gradient(180deg, #ffe9a0, var(--amber));
  box-shadow:
    0 0 0 2px #fff3c4 inset,
    0 0 22px var(--amber-glow);
  z-index: 1;
}

.tape-cell.is-head::after {
  content: "▼";
  position: absolute;
  top: -0.05rem;
  font-size: 0.7rem;
  color: #5a4200;
}

.hint {
  margin: 0.65rem 0 0;
  color: var(--muted);
  font-size: 0.82rem;
}

/* —— Controls —— */
.controls {
  background: var(--ink-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem;
}

.control-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  align-items: center;
}

.speed {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-left: auto;
  color: var(--muted);
  font-size: 0.9rem;
}

.speed input[type="range"] {
  width: min(140px, 30vw);
  accent-color: var(--amber);
}

.speed-val {
  font-family: var(--mono);
  min-width: 1.2rem;
  color: var(--text);
}

.status-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.65rem 1rem;
  margin: 1rem 0 0;
}

.status-grid dt {
  margin: 0;
  font-size: 0.75rem;
  color: var(--muted);
}

.status-grid dd {
  margin: 0.15rem 0 0;
  font-family: var(--mono);
  font-size: 1.05rem;
  font-weight: 500;
}

.status-grid .wide {
  grid-column: 1 / -1;
}

#stat-status[data-status="accept"] {
  color: var(--teal);
}

#stat-status[data-status="reject"],
#stat-status[data-status="stuck"] {
  color: var(--coral);
}

#stat-status[data-status="running"] {
  color: var(--amber);
}

.mono {
  font-family: var(--mono);
  font-size: 0.88rem !important;
  word-break: break-all;
}

/* —— Program editor —— */
.program {
  background: var(--ink-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem;
}

.program-head {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  justify-content: space-between;
  gap: 0.75rem;
}

.program h2 {
  margin: 0;
  font-size: 1.1rem;
}

.example-desc {
  margin: 0.75rem 0 1rem;
  color: var(--muted);
  font-size: 0.92rem;
  max-width: 70ch;
}

.state-fields {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.65rem;
  margin-bottom: 0.85rem;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 0.3rem;
  font-size: 0.8rem;
  color: var(--muted);
}

.field.compact {
  min-width: min(220px, 100%);
}

.field input,
.field select,
.cell-in {
  font-family: var(--mono);
  font-size: 0.92rem;
  color: var(--text);
  background: var(--ink);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0.55rem 0.65rem;
  min-height: 42px;
  width: 100%;
}

.field input:focus,
.field select:focus,
.cell-in:focus {
  outline: 2px solid var(--sky);
  outline-offset: 1px;
  border-color: transparent;
}

.inline {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.inline input {
  flex: 1 1 160px;
}

.table-wrap {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  border: 1px solid var(--line);
  border-radius: 10px;
}

.transitions {
  width: 100%;
  border-collapse: collapse;
  min-width: 520px;
}

.transitions th {
  text-align: left;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--muted);
  padding: 0.55rem 0.5rem;
  background: var(--ink-3);
  border-bottom: 1px solid var(--line);
  white-space: nowrap;
}

.transitions td {
  padding: 0.35rem 0.35rem;
  border-bottom: 1px solid var(--line);
  vertical-align: middle;
}

.transitions tr:last-child td {
  border-bottom: none;
}

.cell-in {
  min-height: 38px;
  padding: 0.4rem 0.45rem;
}

.program-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  margin-top: 0.85rem;
  justify-content: space-between;
}

.footer {
  text-align: center;
  color: var(--muted);
  font-size: 0.8rem;
  padding: 0.5rem 0 0;
}

.toast {
  position: fixed;
  left: 50%;
  bottom: calc(1.25rem + var(--safe-bottom));
  transform: translateX(-50%);
  background: var(--paper);
  color: var(--ink);
  padding: 0.65rem 1.1rem;
  border-radius: 999px;
  font-weight: 600;
  font-size: 0.9rem;
  box-shadow: var(--shadow);
  z-index: 50;
}

@media (max-width: 720px) {
  .app {
    padding: 0.75rem 0.75rem calc(1.5rem + var(--safe-bottom));
    gap: 0.75rem;
  }

  .state-fields {
    grid-template-columns: 1fr;
  }

  .speed {
    margin-left: 0;
    width: 100%;
  }

  .speed input[type="range"] {
    flex: 1;
    width: auto;
  }

  .control-row .btn {
    flex: 1 1 auto;
  }

  .tape-cell {
    width: 2.75rem;
    min-height: 3.8rem;
  }

  .status-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (min-width: 860px) {
  .status-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .status-grid .wide {
    grid-column: 1 / -1;
  }
}

@media (prefers-reduced-motion: reduce) {
  .btn,
  .tape-cell {
    transition: none;
  }
}