:root {
  --bg: #ffffff;
  --fg: #000000;
  --accent: #ffeb3b;
  --shadow: 0 4px 0 #000;
  --shadow-lg: 0 8px 0 #000;
  --border: 3px solid #000;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'Hiragino Sans', 'Yu Gothic UI', sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.5;
  min-height: 100%;
  overflow-x: hidden;
}

#app {
  max-width: 480px;
  margin: 0 auto;
  padding: 24px 16px;
  min-height: 100vh;
}

h1 { font-size: 32px; font-weight: 900; letter-spacing: -1px; margin-bottom: 12px; }
h2 { font-size: 24px; font-weight: 800; margin-bottom: 12px; }
h3 { font-size: 18px; font-weight: 700; margin-bottom: 8px; }
p { margin-bottom: 12px; }
ul { list-style: none; }

/* ----- buttons ----- */
.btn-primary, .btn-secondary {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  width: 100%;
  padding: 16px 24px;
  font-size: 16px;
  font-weight: 700;
  border: var(--border);
  background: var(--bg);
  color: var(--fg);
  cursor: pointer;
  margin-bottom: 12px;
  box-shadow: var(--shadow);
  transition: transform 0.1s, box-shadow 0.1s;
}
.btn-primary { background: var(--accent); }
.btn-big { padding: 24px; font-size: 18px; box-shadow: var(--shadow-lg); }
.btn-primary:active, .btn-secondary:active {
  transform: translate(2px, 2px);
  box-shadow: 0 2px 0 #000;
}
.btn-icon { font-size: 24px; }

/* ----- home ----- */
.home { padding: 32px 0; }
.home-title { font-size: 48px; }
.home-subtitle { font-size: 16px; color: #666; margin-bottom: 32px; }
.home-stat { margin-top: 16px; font-size: 14px; color: #555; text-align: center; }
.home-hint { margin-top: 16px; font-size: 14px; color: #555; text-align: center; }

/* ----- onboarding ----- */
.onboard { padding: 24px 0; }
.onboard-lead { font-size: 18px; margin: 16px 0 24px; line-height: 1.4; }
.onboard-list li {
  padding: 12px 16px;
  border: var(--border);
  margin-bottom: 8px;
  background: #fafafa;
}
.onboard-note { font-size: 14px; color: #666; margin: 16px 0; }

/* ----- session ----- */
.session-banner {
  padding: 12px;
  background: #000;
  color: #fff;
  font-weight: 700;
  text-align: center;
  margin-bottom: 16px;
}
.session-container {
  border: var(--border);
  padding: 24px;
  min-height: 400px;
  background: var(--bg);
  box-shadow: var(--shadow);
}

/* ----- digit-span ----- */
.digit-span-display {
  font-size: 96px;
  font-weight: 900;
  text-align: center;
  padding: 60px 0;
  font-family: monospace;
}
.digit-span-prompt { font-size: 16px; margin-bottom: 16px; }
.digit-span-input {
  width: 100%;
  font-size: 32px;
  text-align: center;
  padding: 16px;
  border: var(--border);
  font-family: monospace;
  margin-bottom: 16px;
}

/* ----- visual-patterns ----- */
.vp-prompt { font-size: 16px; margin-bottom: 16px; }
.vp-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin: 16px 0;
}
.vp-cell {
  aspect-ratio: 1 / 1;
  border: var(--border);
  background: var(--bg);
  cursor: pointer;
}
.vp-cell.on { background: #000; }
.vp-cell.selected { background: var(--accent); }

/* ----- reaction-time ----- */
.rt-screen {
  width: 100%;
  height: 360px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  user-select: none;
  border: var(--border);
}
.rt-wait { background: #f44336; color: #fff; }
.rt-go { background: #4caf50; color: #fff; }
.rt-msg { font-size: 28px; font-weight: 800; }

/* ----- n-back ----- */
.nback-instructions { padding: 16px 0; }
.nback-stimulus {
  font-size: 120px;
  font-weight: 900;
  text-align: center;
  padding: 40px 0;
  font-family: monospace;
}
.nback-tap {
  width: 100%;
  padding: 24px;
  font-size: 20px;
  font-weight: 700;
  border: var(--border);
  background: var(--accent);
  cursor: pointer;
  box-shadow: var(--shadow);
}
.nback-tap:active { transform: translate(2px, 2px); box-shadow: 0 2px 0 #000; }

/* ----- dashboard ----- */
.dashboard { padding: 16px 0; }
.dash-header { margin-bottom: 24px; }
.dash-meta { color: #555; font-size: 14px; }
.dash-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 24px;
}
.metric-tile {
  border: var(--border);
  padding: 16px;
  background: var(--bg);
  box-shadow: var(--shadow);
}
.metric-tile.locked { background: #f5f5f5; opacity: 0.7; }
.metric-label { font-size: 12px; font-weight: 700; margin-bottom: 8px; text-transform: uppercase; }
.metric-value { font-size: 28px; font-weight: 900; font-family: monospace; }
.metric-sub { font-size: 11px; color: #666; margin-top: 4px; }
.metric-spark { margin-top: 8px; width: 100%; }
.lock-icon { font-size: 24px; margin-bottom: 8px; }
.progress-bar {
  width: 100%;
  height: 8px;
  border: 2px solid #000;
  margin-top: 8px;
}
.progress-fill { height: 100%; background: var(--accent); }

/* ----- responsive ----- */
@media (min-width: 768px) {
  #app { max-width: 600px; }
}