:root {
  color-scheme: light;
  --ink: #132a42;
  --muted: #526579;
  --page: #e8f1f3;
  --paper: #fbfdfd;
  --line: #b9cbd2;
  --deep: #17324d;
  --deep-hover: #0f263c;
  --focus: #e2563f;
  --soft-blue: #d8e9ed;
  --radius-lg: 26px;
  --radius-md: 16px;
  --shadow: 0 18px 46px rgba(19, 42, 66, 0.14);
  font-family: "Yu Gothic UI", "Hiragino Kaku Gothic ProN", Meiryo, system-ui, sans-serif;
  font-size: 16px;
}

* { box-sizing: border-box; }

html { min-width: 280px; }

body {
  margin: 0;
  min-height: 100svh;
  color: var(--ink);
  background:
    radial-gradient(circle at 12% 8%, rgba(255, 255, 255, 0.9) 0 7rem, transparent 7.1rem),
    linear-gradient(145deg, #edf5f5, var(--page));
}

button, input { font: inherit; }

button { touch-action: manipulation; }

button:focus-visible,
input:focus-visible + .difficulty-card {
  outline: 4px solid var(--focus);
  outline-offset: 3px;
}

[hidden] { display: none !important; }

.app-shell {
  width: min(100%, 46rem);
  margin: 0 auto;
  padding: 1.25rem 0.75rem 2rem;
}

.site-header {
  position: relative;
  padding: 0.25rem 0.3rem 1rem 3.4rem;
}

.site-header h1 {
  margin: 0.08rem 0 0;
  font-size: clamp(1.7rem, 7vw, 2.25rem);
  line-height: 1.12;
  letter-spacing: 0.08em;
}

.eyebrow {
  margin: 0;
  color: var(--muted);
  font-size: 0.875rem;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.brand-mark {
  position: absolute;
  left: 0.35rem;
  top: 0.35rem;
  display: grid;
  grid-template-columns: repeat(2, 1rem);
  gap: 0.22rem;
  transform: rotate(-4deg);
}

.brand-mark span {
  display: block;
  width: 1rem;
  height: 1rem;
  border: 2px solid var(--deep);
  border-radius: 0.28rem;
  background: #fff;
}

.brand-mark span:nth-child(2) { background: #ffd166; }
.brand-mark span:nth-child(3) { grid-column: 2; background: #77c7d7; }

.panel {
  overflow: hidden;
  border: 1px solid rgba(145, 170, 180, 0.7);
  border-radius: var(--radius-lg);
  background: rgba(251, 253, 253, 0.96);
  box-shadow: var(--shadow);
}

.start-panel,
.end-panel { padding: clamp(1.35rem, 5vw, 2.5rem); }

.intro-copy h2,
.end-panel h2 {
  margin: 0;
  font-size: clamp(1.55rem, 6vw, 2.25rem);
  line-height: 1.4;
  letter-spacing: 0.03em;
}

.intro-copy p {
  max-width: 30rem;
  margin: 0.65rem 0 0;
  color: var(--muted);
  line-height: 1.75;
}

.difficulty-picker {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  margin: 1.75rem 0 1.25rem;
  padding: 0;
  border: 0;
}

.difficulty-picker legend {
  grid-column: 1 / -1;
  margin-bottom: 0.65rem;
  font-weight: 800;
}

.difficulty-option { position: relative; }
.difficulty-option input { position: absolute; opacity: 0; }

.difficulty-card {
  display: flex;
  min-height: 5rem;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
  border: 2px solid var(--line);
  border-radius: var(--radius-md);
  background: #fff;
  cursor: pointer;
}

.difficulty-card strong { font-size: 1.05rem; }
.difficulty-card small { color: var(--muted); font-size: 0.875rem; font-weight: 700; }

.difficulty-option input:checked + .difficulty-card {
  border-color: var(--deep);
  background: var(--soft-blue);
  box-shadow: inset 0 0 0 2px #fff;
}

.button {
  min-height: 3rem;
  padding: 0.7rem 1rem;
  border: 2px solid transparent;
  border-radius: 999px;
  font-weight: 800;
  line-height: 1.25;
  cursor: pointer;
  transition: transform 150ms ease, background-color 150ms ease, border-color 150ms ease;
}

.button:not(:disabled):active { transform: translateY(1px); }
.button:disabled { cursor: default; opacity: 0.48; }
.button-wide { width: 100%; }

.button-primary,
.button-finish {
  color: #fff;
  background: var(--deep);
}

.button-primary:hover,
.button-finish:hover { background: var(--deep-hover); }

.button-secondary {
  color: var(--ink);
  border-color: var(--line);
  background: #fff;
}

.button-secondary:hover:not(:disabled) { border-color: var(--deep); background: #eef5f6; }

.button-quiet {
  color: var(--ink);
  border-color: transparent;
  background: transparent;
  text-decoration: underline;
  text-underline-offset: 0.25rem;
}

.keyboard-note {
  margin: 1rem 0 0;
  color: var(--muted);
  font-size: 0.875rem;
  line-height: 1.6;
}

.game-panel { padding: clamp(1rem, 4vw, 1.75rem); }

.game-topline,
.section-heading {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 1rem;
}

.round-label {
  margin: 0 0 0.2rem;
  color: var(--muted);
  font-size: 0.875rem;
  font-weight: 800;
}

.game-topline h2 { margin: 0; font-size: clamp(1.35rem, 5vw, 1.8rem); }

.difficulty-badge {
  flex: 0 0 auto;
  margin: 0;
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  color: var(--deep);
  background: var(--soft-blue);
  font-size: 0.875rem;
  font-weight: 800;
}

.progress-track {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.4rem;
  margin: 1rem 0 1.25rem;
}

.progress-track span {
  height: 0.42rem;
  border-radius: 999px;
  background: #d7e1e4;
}

.progress-track span.is-current { background: #eaa93f; }
.progress-track span.is-done { background: #4b9a82; }

.reference-area {
  display: grid;
  grid-template-columns: minmax(6.5rem, 0.7fr) minmax(9rem, 1fr);
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.1rem;
  padding: 0.8rem 1rem;
  border-radius: var(--radius-md);
  background: #eaf2f4;
}

.section-heading h3 { margin: 0; font-size: 1rem; }
.section-heading p { margin: 0; color: var(--muted); font-size: 0.875rem; }
.reference-area .section-heading { display: block; }
.reference-area .section-heading p { margin-top: 0.25rem; }

.target-board,
.game-board {
  --grid-size: 2;
  display: grid;
  grid-template-columns: repeat(var(--grid-size), 1fr);
}

.target-board {
  width: min(100%, 10rem);
  margin-left: auto;
  gap: 0.25rem;
}

.target-tile {
  display: grid;
  aspect-ratio: 1;
  place-items: center;
  border: 2px solid rgba(19, 42, 66, 0.44);
  border-radius: 0.55rem;
  color: var(--ink);
  background: var(--tile-color);
  font-size: clamp(0.95rem, 4.2vw, 1.45rem);
  font-weight: 900;
}

.play-area .section-heading { margin-bottom: 0.65rem; }

.game-board {
  width: min(100%, 30rem);
  margin: 0 auto;
  gap: clamp(0.42rem, 2vw, 0.7rem);
}

.tile {
  position: relative;
  display: flex;
  aspect-ratio: 1;
  min-width: 0;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.1rem;
  padding: 0.2rem;
  border: 3px solid rgba(19, 42, 66, 0.55);
  border-radius: clamp(0.7rem, 3vw, 1.15rem);
  color: var(--ink);
  background: var(--tile-color);
  box-shadow: 0 5px 0 rgba(19, 42, 66, 0.18);
  cursor: pointer;
  transition: transform 180ms ease, box-shadow 180ms ease, outline-color 180ms ease;
}

.tile:hover:not(:disabled) { transform: translateY(-2px); }
.tile:disabled { cursor: default; }

.tile-symbol {
  font-size: clamp(1.55rem, 10vw, 3.25rem);
  font-weight: 900;
  line-height: 1;
}

.tile-name {
  font-size: clamp(0.875rem, 3.6vw, 0.95rem);
  font-weight: 800;
  line-height: 1.2;
}

.tile.is-selected {
  z-index: 1;
  outline: 5px solid var(--deep);
  outline-offset: 2px;
  transform: translateY(-3px);
  box-shadow: 0 8px 0 rgba(19, 42, 66, 0.2);
}

.tile.is-hint {
  outline: 5px dashed var(--focus);
  outline-offset: 2px;
}

.tool-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
  margin-top: 1.2rem;
}

.tool-row .button { min-width: 0; padding-inline: 0.4rem; font-size: 0.875rem; }

.status-message {
  min-height: 1.6em;
  margin: 0.8rem 0 0;
  color: var(--muted);
  text-align: center;
  font-weight: 700;
  line-height: 1.6;
}

.round-complete {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 0.75rem;
  margin-top: 1rem;
  padding: 0.85rem;
  border: 2px solid #70a996;
  border-radius: var(--radius-md);
  background: #e3f1ec;
  animation: settle-in 450ms ease-out both;
}

.round-complete strong { font-size: 1.05rem; }
.round-complete p { margin: 0.15rem 0 0; color: var(--muted); font-size: 0.875rem; }

.complete-symbol {
  display: grid;
  width: 2.6rem;
  aspect-ratio: 1;
  place-items: center;
  border-radius: 50%;
  color: #fff;
  background: #397d69;
  font-size: 1.35rem;
  font-weight: 900;
}

.end-panel {
  text-align: center;
  animation: settle-in 650ms ease-out both;
}

.settled-mark {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  margin-bottom: 1.4rem;
}

.settled-mark span {
  display: grid;
  width: 3rem;
  aspect-ratio: 1;
  place-items: center;
  border: 2px solid var(--ink);
  border-radius: 0.8rem;
  background: #ffd166;
  font-size: 1.25rem;
  font-weight: 900;
}

.settled-mark span:nth-child(2) { background: #7fcfda; }
.settled-mark span:nth-child(3) { background: #ef947d; }

.end-kicker { margin: 0 0 0.5rem; color: #397d69; font-weight: 900; }
.end-panel h2 { font-size: clamp(1.7rem, 7vw, 2.5rem); }
.end-panel > p:not(.end-kicker) { margin: 1rem 0 0; color: var(--muted); line-height: 1.7; }

.end-actions {
  display: flex;
  max-width: 22rem;
  flex-direction: column;
  gap: 0.5rem;
  margin: 1.75rem auto 0;
}

.button-finish { min-height: 3.5rem; font-size: 1.05rem; }

.site-footer {
  padding: 1.25rem 0.75rem 0;
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.6;
  text-align: center;
}

.site-footer p { margin: 0.15rem 0; }

.site-footer p:first-child {
  font-weight: 800;
  letter-spacing: 0.08em;
}

@keyframes settle-in {
  from { opacity: 0; transform: translateY(10px) scale(0.985); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}

@media (max-width: 380px) {
  .app-shell { padding-inline: 0.5rem; }
  .game-panel { padding: 0.8rem; }
  .reference-area { grid-template-columns: minmax(5.5rem, 0.65fr) minmax(8rem, 1fr); padding-inline: 0.7rem; }
  .tool-row .button span { display: block; }
}

@media (min-width: 48rem) {
  .app-shell { padding-top: 2rem; }
  .game-panel { padding-inline: 2.5rem; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    scroll-behavior: auto !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}