:root {
  --bg: #f5f7fb;
  --ink: #1f2430;
  --primary: #3b6fed;
  --primary-ink: #ffffff;
  --correct: #2fa84f;
  --wrong: #e0483e;
  --card: #ffffff;
  --border: #d8dee9;
  --typed: #5b9df0;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "PingFang TC", "Segoe UI", sans-serif;
  -webkit-tap-highlight-color: transparent;
  user-select: none;
}

#app {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
}

.screen {
  width: 100%;
  max-width: 640px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
}

.screen[hidden] {
  display: none;
}

h1 {
  font-size: clamp(1.5rem, 5vw, 2.25rem);
  margin: 0;
  text-align: center;
}

h2 {
  font-size: 1.1rem;
  margin: 0 0 0.75rem 0;
  color: #555;
}

.settings-block {
  width: 100%;
  background: var(--card);
  border-radius: 16px;
  padding: 1rem 1.25rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.grid-9 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.6rem;
}

.grid-9 button {
  padding: 0.4rem 0;
  font-size: 1.2rem;
  font-weight: 600;
  border-radius: 10px;
  border: 2px solid var(--border);
  background: var(--bg);
  color: var(--ink);
  cursor: pointer;
}

.grid-9 button.selected {
  background: var(--primary);
  border-color: var(--primary);
  color: var(--primary-ink);
}

#question-count {
  width: 100%;
  font-size: 1.5rem;
  padding: 0.6rem;
  border-radius: 12px;
  border: 2px solid var(--border);
  text-align: center;
}

.mode-toggle {
  display: flex;
  gap: 0.6rem;
}

.mode-btn {
  flex: 1;
  padding: 0.9rem;
  font-size: 1.05rem;
  border-radius: 12px;
  border: 2px solid var(--border);
  background: var(--bg);
  cursor: pointer;
}

.mode-btn.selected {
  background: var(--primary);
  border-color: var(--primary);
  color: var(--primary-ink);
  font-weight: 600;
}

.primary-btn {
  width: 100%;
  padding: 1rem;
  font-size: 1.25rem;
  font-weight: 700;
  border-radius: 14px;
  border: none;
  background: var(--primary);
  color: var(--primary-ink);
  cursor: pointer;
}

.primary-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.secondary-btn {
  flex: 1;
  padding: 1rem;
  font-size: 1.1rem;
  border-radius: 14px;
  border: 2px solid var(--border);
  background: var(--card);
  color: var(--ink);
  cursor: pointer;
}

.error-msg {
  color: var(--wrong);
  font-weight: 600;
  margin: 0;
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 1.05rem;
  margin-bottom: 0.6rem;
  cursor: pointer;
}

.checkbox-row input {
  width: 1.3rem;
  height: 1.3rem;
}

#time-limit-seconds {
  width: 100%;
  font-size: 1.25rem;
  padding: 0.5rem;
  border-radius: 12px;
  border: 2px solid var(--border);
  text-align: center;
}

#time-limit-seconds:disabled {
  opacity: 0.5;
}

.timer {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--primary);
}

.timer.timer-low {
  color: var(--wrong);
}

.progress {
  font-size: 1.1rem;
  color: #666;
}

.question {
  font-size: clamp(3rem, 15vw, 7rem);
  font-weight: 800;
  text-align: center;
  line-height: 1;
}

.feedback {
  font-size: 1.4rem;
  font-weight: 700;
  padding: 0.5rem 1.5rem;
  border-radius: 999px;
}

.feedback.correct {
  color: var(--correct);
  background: rgba(47,168,79,0.12);
}

.feedback.wrong {
  color: var(--wrong);
  background: rgba(224,72,62,0.12);
}

.answer-area {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.answer-area[hidden] {
  display: none;
}

.keypad-display {
  width: 100%;
  min-height: 5.5rem;
  font-size: clamp(3rem, 16vw, 5rem);
  font-weight: 700;
  color: var(--typed);
  text-align: center;
  background: var(--card);
  border-radius: 14px;
  border: 2px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
}

.keypad-grid {
  width: 100%;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.6rem;
}

.keypad-grid button {
  padding: 1.1rem;
  font-size: clamp(2rem, 10vw, 3.2rem);
  font-weight: 600;
  border-radius: 14px;
  border: 2px solid var(--border);
  background: var(--card);
  cursor: pointer;
}

.keypad-actions {
  width: 100%;
  display: flex;
  gap: 0.6rem;
}

.choice-grid {
  width: 100%;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.8rem;
}

.choice-grid button {
  padding: 1.5rem;
  font-size: clamp(3rem, 18vw, 6rem);
  font-weight: 700;
  border-radius: 16px;
  border: 2px solid var(--border);
  background: var(--card);
  cursor: pointer;
}

.choice-grid button:disabled,
.keypad-grid button:disabled,
.grid-9 button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.score {
  font-size: clamp(4rem, 20vw, 7rem);
  font-weight: 800;
  color: var(--wrong);
  text-shadow: 0 3px 0 rgba(0,0,0,0.08);
  line-height: 1;
}

.stats {
  width: 100%;
  background: var(--card);
  border-radius: 16px;
  padding: 1.25rem;
  font-size: 1.15rem;
  line-height: 1.8;
  text-align: center;
}

@media (min-width: 480px) {
  .grid-9 button {
    font-size: 1.75rem;
  }
}