:root {
  --bg: #faf7f0; --surface: #fff; --ink: #1a1a1a; --muted: #6b6b6b;
  --line: #e6e0d4; --accent: #2563eb; --radius: 14px;
  --green: #22c55e; --green-bg: #dcfce7; --green-ink: #166534;
  --yellow: #eab308; --yellow-bg: #fef9c3; --yellow-ink: #854d0e;
  --gray: #9ca3af; --gray-bg: #f3f4f6; --gray-ink: #4b5563;
  --cell-size: min(26vw, 110px);
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14140f; --surface: #1e1e18; --ink: #f2efe6; --muted: #a19b8c;
    --line: #2e2e26; --accent: #60a5fa;
    --green-bg: #14532d; --green-ink: #bbf7d0;
    --yellow-bg: #713f12; --yellow-ink: #fef08a;
    --gray-bg: #374151; --gray-ink: #d1d5db;
  }
}
* { box-sizing: border-box; margin: 0; }
html, body { height: 100%; }
body {
  background: var(--bg); color: var(--ink);
  font: 16px/1.4 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased; overscroll-behavior: none;
}
.app {
  max-width: 480px; margin: 0 auto; min-height: 100svh;
  padding: max(12px, env(safe-area-inset-top)) 16px max(12px, env(safe-area-inset-bottom));
  display: flex; flex-direction: column; align-items: center; gap: 14px;
}
.header { text-align: center; }
.logo { font-size: clamp(28px, 8vw, 40px); font-weight: 800; letter-spacing: -.02em; margin: 0; }
.tagline { color: var(--muted); margin: 4px 0 0; font-size: .92rem; }

/* axis labels */
.axis-labels {
  position: relative; width: calc(var(--cell-size) * 3 + 16px);
  height: 18px; margin-bottom: -6px;
}
.axis-label { position: absolute; font-size: .7rem; color: var(--muted); text-transform: uppercase; letter-spacing: .06em; }
.col-label.west { left: 0; top: 0; }
.col-label.east { right: 0; top: 0; }
.row-label { writing-mode: vertical-lr; }
.row-label.north { display: none; }
.row-label.south { display: none; }

/* board */
.board {
  display: grid; grid-template-columns: repeat(3, var(--cell-size));
  grid-template-rows: repeat(3, var(--cell-size)); gap: 4px;
  position: relative;
}
.cell {
  width: var(--cell-size); height: var(--cell-size);
  border: 2px dashed var(--line); border-radius: 10px;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  position: relative; transition: border-color .15s, background .25s;
  font-size: clamp(11px, 3.2vw, 15px); font-weight: 600;
  text-align: center; line-height: 1.2; padding: 6px;
  cursor: default; user-select: none;
}
.cell.drop-target { border-color: var(--accent); background: rgba(37,99,235,.08); }
.cell.filled { border-style: solid; border-color: var(--line); background: var(--surface); cursor: grab; }
.cell.locked { cursor: default; }
.cell.center-lock {
  border-style: solid; border-color: var(--accent);
  background: rgba(37,99,235,.08); cursor: default;
}
.cell .city-name { pointer-events: none; display: block; }
.cell .country { font-size: .7em; color: var(--muted); font-weight: 400; display: block; pointer-events: none; margin-top: 1px; }
.cell .arrow {
  position: absolute; font-size: 14px; pointer-events: none; opacity: .85;
}
.cell .arrow.arrow-left { left: 2px; top: 50%; transform: translateY(-50%); }
.cell .arrow.arrow-right { right: 2px; top: 50%; transform: translateY(-50%); }
.cell .arrow.arrow-up { top: 2px; left: 50%; transform: translateX(-50%); }
.cell .arrow.arrow-down { bottom: 2px; left: 50%; transform: translateX(-50%); }

/* feedback colors */
.cell.fb-correct { background: var(--green-bg); border-color: var(--green); color: var(--green-ink); }
.cell.fb-row { background: var(--yellow-bg); border-color: var(--yellow); color: var(--yellow-ink); }
.cell.fb-col { background: var(--yellow-bg); border-color: var(--yellow); color: var(--yellow-ink); }
.cell.fb-wrong { background: var(--gray-bg); border-color: var(--gray); color: var(--gray-ink); }

/* tray */
.tray {
  display: flex; flex-wrap: wrap; gap: 6px; justify-content: center;
  min-height: 40px; width: 100%; max-width: calc(var(--cell-size) * 3 + 16px);
}
.chip {
  padding: 6px 10px; border-radius: 8px; font-size: clamp(10px, 2.8vw, 13px);
  font-weight: 600; background: var(--surface); border: 1.5px solid var(--line);
  cursor: grab; user-select: none; touch-action: none;
  line-height: 1.2; text-align: center; transition: opacity .15s, transform .15s;
}
.chip .country { font-size: .65em; color: var(--muted); font-weight: 400; display: block; }
.chip.dragging { opacity: .4; transform: scale(.95); }
.chip.selected { border-color: var(--accent); box-shadow: 0 0 0 2px rgba(37,99,235,.25); }

/* drag ghost */
.drag-ghost {
  position: fixed; pointer-events: none; z-index: 100;
  padding: 6px 10px; border-radius: 8px; font-size: 13px; font-weight: 600;
  background: var(--surface); border: 2px solid var(--accent);
  box-shadow: 0 4px 16px rgba(0,0,0,.18); transform: translate(-50%, -50%);
  line-height: 1.2; text-align: center;
}
.drag-ghost .country { font-size: .65em; color: var(--muted); font-weight: 400; display: block; }

/* controls */
.controls { display: flex; align-items: center; gap: 14px; width: 100%; max-width: calc(var(--cell-size) * 3 + 16px); }
.status { flex: 1; font-size: .85rem; color: var(--muted); }
.status b { color: var(--ink); }
.btn {
  padding: 10px 20px; font-size: .95rem; font-weight: 700; color: #fff;
  background: var(--accent); border: none; border-radius: 10px; cursor: pointer;
}
.btn:disabled { opacity: .35; cursor: not-allowed; }
.submit-btn { min-width: 90px; }

/* result */
.result {
  display: flex; flex-direction: column; align-items: center; gap: 10px;
  padding: 16px; background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); width: 100%; max-width: calc(var(--cell-size) * 3 + 40px);
}
.result-title { font-size: 1.2rem; }
.result-detail { color: var(--muted); font-size: .9rem; margin: 0; }
.result-grid { font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 1.4rem; line-height: 1.6; text-align: center; }
.copied { color: var(--accent); font-size: .85rem; }
.btn-link { background: none; border: none; color: var(--accent); cursor: pointer; font-size: .85rem; text-decoration: underline; }
.help {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 14px 16px; font-size: .88rem; line-height: 1.5; color: var(--muted);
  max-width: calc(var(--cell-size) * 3 + 40px);
}
.help b { color: var(--ink); }
.help ul { padding-left: 18px; margin: 6px 0 0; }
.help li { margin: 2px 0; }
.help p { margin: 0 0 6px; }
.foot { margin-top: auto; text-align: center; color: var(--muted); font-size: .78rem; padding: 8px 0; }
.foot a { color: var(--muted); }