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

body {
  font-family: 'Inter', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, "Hiragino Kaku Gothic ProN", "Hiragino Sans", "Meiryo", "MS PGothic", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-primary);
  transition: background-color var(--transition-speed), color var(--transition-speed);
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

#app {
  flex: 1;
  display: flex;
  flex-direction: column;
  max-width: 800px;
  margin: 0 auto;
  padding: 1rem;
  width: 100%;
}

h1, h2, h3 {
  margin-bottom: 1rem;
  text-align: center;
}

.screen {
  display: none;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
  animation: fadeIn 0.3s ease-in-out;
}

.screen.active {
  display: flex;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.hidden {
  display: none !important;
}

button {
  cursor: pointer;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  transition: transform 0.1s active, opacity 0.2s;
}

button:active {
  transform: scale(0.98);
}

input[type="text"] {
  width: 100%;
  padding: 0.75rem;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background-color: var(--surface-color);
  color: var(--text-primary);
  font-size: 1.25rem;
  text-align: center;
}

input:focus {
  outline: 2px solid var(--accent-color);
}