:root {
  --bg: #1a1f2e;
  --surface: #252b3d;
  --surface2: #2f3649;
  --text: #eef1f8;
  --muted: #9aa3b8;
  --accent: #5b8def;
  --accent-dim: #3d6fd4;
  --success: #4ade80;
  --danger: #f87171;
  --radius: 14px;
  --tap: 48px;
  --safe-top: env(safe-area-inset-top, 0);
  --safe-bottom: env(safe-area-inset-bottom, 0);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

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

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

body {
  margin: 0;
  min-height: 100dvh;
  background: var(--bg);
  color: var(--text);
  line-height: 1.45;
  padding: calc(12px + var(--safe-top)) 16px calc(16px + var(--safe-bottom));
  overscroll-behavior: none;
}

.app {
  max-width: 420px;
  margin: 0 auto;
}

.header {
  text-align: center;
  margin-bottom: 1.25rem;
}

.logo {
  margin: 0;
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.tagline {
  margin: 0.25rem 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.screen {
  display: none;
}

.screen--active {
  display: block;
}

.screen:not(.screen--active) {
  display: none !important;
}

.stats {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1rem;
  margin-bottom: 1.25rem;
  font-size: 0.9rem;
}

.stats__row {
  display: flex;
  justify-content: space-between;
  gap: 0.5rem;
  margin-bottom: 0.35rem;
}

.stats__row:last-child {
  margin-bottom: 0;
}

.stats strong {
  color: var(--accent);
}

.section-title {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
  margin: 1.5rem 0 0.75rem;
}

.hint {
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
  margin: 0.5rem 0 0;
}

.game-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.game-list__item {
  width: 100%;
}

.site-footer {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--surface2);
  text-align: center;
}

.btn--reset {
  width: 100%;
  font-size: 0.85rem;
  color: var(--muted);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: var(--tap);
  padding: 0.65rem 1.25rem;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
  transition: transform 0.1s, opacity 0.15s;
}

.btn:active {
  transform: scale(0.97);
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn--primary {
  background: var(--accent);
  color: #fff;
  width: 100%;
}

.btn--secondary {
  background: var(--surface2);
  color: var(--text);
  width: 100%;
}

.btn--ghost {
  background: transparent;
  color: var(--text);
  min-width: var(--tap);
  padding: 0.5rem;
}

.btn--large {
  font-size: 1.1rem;
  padding: 1rem;
}

.btn--game {
  width: 100%;
  background: var(--surface2);
  color: var(--text);
  text-align: left;
  justify-content: flex-start;
  gap: 0.75rem;
}

.btn--game .emoji {
  font-size: 1.4rem;
}

.game-top {
  display: flex;
  align-items: flex-start;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.game-meta {
  flex: 1;
  min-width: 0;
}

.game-title {
  margin: 0;
  font-size: 1.15rem;
}

.game-progress {
  margin: 0.2rem 0 0;
  font-size: 0.8rem;
  color: var(--muted);
}

.timer {
  font-variant-numeric: tabular-nums;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--accent);
  min-width: 2.5rem;
  text-align: right;
}

.game-area {
  min-height: 280px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.game-hint {
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
  margin: 1rem 0 0;
}

.game-settings {
  margin-top: 1rem;
}

.game-settings[hidden] {
  display: none;
}

/* Memory */
.memory-settings {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 0.65rem 0.75rem;
  background: var(--surface);
  border-radius: var(--radius);
  font-size: 0.85rem;
}

.memory-settings__label {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  color: var(--muted);
  cursor: default;
}

.memory-settings__input {
  width: 4.5rem;
  padding: 0.4rem 0.5rem;
  border: 1px solid var(--surface2);
  border-radius: 8px;
  background: var(--surface2);
  color: var(--text);
  font-size: 1rem;
  text-align: center;
}

.memory-settings__input:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
}

.memory-grid {
  display: grid;
  gap: 8px;
  width: 100%;
  max-width: 340px;
}

.memory-card {
  aspect-ratio: 1;
  border: none;
  border-radius: 10px;
  background: var(--surface2);
  font-size: 1.5rem;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.memory-card--hidden {
  color: transparent;
}

.memory-card--matched {
  opacity: 0.35;
  pointer-events: none;
}

.memory-card:not(.memory-card--hidden):not(:disabled) {
  background: var(--accent-dim);
}

.memory-actions {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  width: 100%;
  max-width: 340px;
  margin-top: 1rem;
}

.memory-remember-btn,
.memory-hint-btn {
  width: 100%;
}

.memory-action--hidden {
  display: none !important;
}

/* Stroop */
.stroop-word {
  font-size: clamp(2rem, 12vw, 3rem);
  font-weight: 800;
  margin: 0.5rem 0 1.25rem;
  text-align: center;
}

.stroop-colors {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  width: 100%;
}

.stroop-swatch {
  min-height: 64px;
  border: 3px solid transparent;
  border-radius: var(--radius);
  cursor: pointer;
}

/* Math */
.math-problem {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.math-input-row {
  display: flex;
  gap: 8px;
  width: 100%;
}

.math-input {
  flex: 1;
  min-height: var(--tap);
  font-size: 1.25rem;
  text-align: center;
  border: 2px solid var(--surface2);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
}

.math-keypad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  width: 100%;
  margin-top: 10px;
}

.math-key {
  min-height: 52px;
  font-size: 1.2rem;
  border: none;
  border-radius: 10px;
  background: var(--surface2);
  color: var(--text);
}

/* Simon */
.simon-pad {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  width: 100%;
  max-width: 280px;
}

.simon-btn {
  aspect-ratio: 1.2;
  border: none;
  border-radius: var(--radius);
  opacity: 0.85;
  cursor: pointer;
}

.simon-btn--active {
  opacity: 1;
  filter: brightness(1.35);
  transform: scale(1.03);
}

.simon-btn--0 { background: #ef4444; }
.simon-btn--1 { background: #3b82f6; }
.simon-btn--2 { background: #22c55e; }
.simon-btn--3 { background: #eab308; }

.simon-status {
  text-align: center;
  margin-bottom: 1rem;
  color: var(--muted);
}

/* Result */
.result-title {
  text-align: center;
  margin: 2rem 0 0.5rem;
}

.result-score {
  text-align: center;
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  margin: 0;
}

.result-detail {
  text-align: center;
  color: var(--muted);
  margin: 0.5rem 0 2rem;
}

.result-actions {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.result-action--hidden {
  display: none !important;
}

.btn[hidden] {
  display: none !important;
}

.feedback {
  text-align: center;
  font-size: 1.1rem;
  min-height: 1.5em;
}

.feedback--ok { color: var(--success); }
.feedback--bad { color: var(--danger); }

/* N-back */
.nback-letter {
  font-size: clamp(4rem, 20vw, 6rem);
  font-weight: 800;
  letter-spacing: 0.05em;
  margin: 0 0 1rem;
  color: var(--accent);
  min-height: 1.2em;
  text-align: center;
}

.nback-btns {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  width: 100%;
  margin-top: 0.5rem;
}

.nback-btn {
  min-height: 64px;
  font-size: 1.15rem;
}

/* Reaction */
.reaction-circle {
  width: min(260px, 80vw);
  height: min(260px, 80vw);
  border-radius: 50%;
  border: none;
  font-size: 1.4rem;
  font-weight: 700;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  transition: background 0.15s, transform 0.1s;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  margin-bottom: 1rem;
}

.reaction-circle--wait {
  background: var(--surface2);
  color: var(--muted);
}

.reaction-circle--go {
  background: var(--success);
  color: #111;
  transform: scale(1.04);
}

.reaction-circle:active {
  transform: scale(0.97);
}

/* Anagram */
.anagram-scramble {
  font-size: clamp(2rem, 12vw, 3.5rem);
  font-weight: 800;
  letter-spacing: 0.12em;
  text-align: center;
  color: var(--accent);
  margin: 0.5rem 0 1rem;
  word-break: break-all;
}

/* Puzzle 15 */
.puzzle-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
  width: 100%;
  max-width: 320px;
}

.puzzle-tile {
  aspect-ratio: 1;
  border: none;
  border-radius: 10px;
  background: var(--surface2);
  color: var(--text);
  font-size: 1.3rem;
  font-weight: 700;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  transition: background 0.1s, transform 0.08s;
}

.puzzle-tile:hover:not(:disabled) {
  background: var(--accent-dim);
}

.puzzle-tile:active:not(:disabled) {
  transform: scale(0.94);
}

.puzzle-tile--blank {
  background: transparent;
  cursor: default;
}

.puzzle-moves {
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 0.75rem;
}

/* Odd one */
.oddone-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  width: 100%;
  max-width: 320px;
}

.oddone-cell {
  aspect-ratio: 1;
  border: none;
  border-radius: 10px;
  background: var(--surface2);
  color: var(--text);
  font-size: 1.6rem;
  cursor: pointer;
}

.oddone-cell--ok { outline: 2px solid var(--success); }
.oddone-cell--bad { outline: 2px solid var(--danger); }

/* Sequence memory */
.sequence-display {
  margin: 0 0 1rem;
  font-size: clamp(1.9rem, 10vw, 2.8rem);
  font-weight: 800;
  letter-spacing: 0.12em;
  color: var(--accent);
}

.sequence-options {
  width: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.sequence-option {
  min-height: 56px;
  border: none;
  border-radius: 10px;
  background: var(--surface2);
  color: var(--text);
  font-size: 1.15rem;
  font-variant-numeric: tabular-nums;
  cursor: pointer;
}

.sequence-option--ok { background: #19613b; }
.sequence-option--bad { background: #7a2323; }

/* Compare numbers */
.compare-row {
  width: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.compare-choice {
  min-height: 104px;
  border: none;
  border-radius: 12px;
  background: var(--surface2);
  color: var(--text);
  font-size: clamp(2rem, 12vw, 2.8rem);
  font-weight: 700;
  cursor: pointer;
}

.compare-choice--ok { background: #19613b; }
.compare-choice--bad { background: #7a2323; }

@media (prefers-reduced-motion: reduce) {
  .btn,
  .simon-btn,
  .reaction-circle,
  .puzzle-tile,
  .compare-choice {
    transition: none;
  }
}