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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background-color: #f5f5f5;
  color: #333;
  min-height: 100vh;
}

#app {
  max-width: 480px;
  margin: 0 auto;
  padding: 20px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  text-align: center;
  padding: 20px 0;
}

header h1 {
  color: #4CAF50;
  font-size: 2rem;
}

.subtitle {
  color: #666;
  font-size: 0.9rem;
  margin-top: 5px;
}

main {
  flex: 1;
}

.view {
  display: none;
}

.view.active {
  display: block;
}

/* Home View */
.streak-info {
  background: linear-gradient(135deg, #4CAF50, #81C784);
  color: white;
  border-radius: 16px;
  padding: 30px;
  text-align: center;
  margin-bottom: 20px;
}

.streak-label {
  display: block;
  font-size: 0.9rem;
  opacity: 0.9;
}

.streak-count {
  font-size: 4rem;
  font-weight: bold;
  display: block;
  line-height: 1.2;
}

.streak-unit {
  font-size: 1rem;
  opacity: 0.9;
}

.primary-btn {
  width: 100%;
  padding: 16px;
  background-color: #4CAF50;
  color: white;
  border: none;
  border-radius: 12px;
  font-size: 1.1rem;
  cursor: pointer;
  transition: background-color 0.2s;
}

.primary-btn:hover {
  background-color: #45a049;
}

.primary-btn:disabled {
  background-color: #ccc;
  cursor: not-allowed;
}

.menu {
  display: flex;
  gap: 10px;
  margin-top: 20px;
}

.menu-btn {
  flex: 1;
  padding: 14px;
  background-color: white;
  border: 2px solid #4CAF50;
  color: #4CAF50;
  border-radius: 12px;
  font-size: 1rem;
  cursor: pointer;
  transition: all 0.2s;
}

.menu-btn:hover {
  background-color: #4CAF50;
  color: white;
}

/* Practice View */
#practice-view h2 {
  color: #4CAF50;
  margin-bottom: 20px;
  text-align: center;
}

#question-container {
  background: white;
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 20px;
  min-height: 150px;
}

.placeholder {
  color: #999;
  text-align: center;
  padding: 40px 0;
}

.subjects {
  display: flex;
  gap: 10px;
}

.subject-btn {
  flex: 1;
  padding: 12px;
  background-color: white;
  border: 1px solid #ddd;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
}

.subject-btn:hover {
  border-color: #4CAF50;
  color: #4CAF50;
}

.subject-btn.active {
  background-color: #4CAF50;
  color: white;
  border-color: #4CAF50;
}

/* Progress View */
#progress-view h2 {
  color: #4CAF50;
  margin-bottom: 20px;
  text-align: center;
}

#history-container {
  background: white;
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 20px;
}

.checkin-item {
  padding: 10px 0;
  border-bottom: 1px solid #eee;
  display: flex;
  justify-content: space-between;
}

.checkin-item:last-child {
  border-bottom: none;
}

.back-btn {
  width: 100%;
  padding: 12px;
  background-color: #f0f0f0;
  border: none;
  border-radius: 8px;
  cursor: pointer;
}

.back-btn:hover {
  background-color: #e0e0e0;
}

/* Footer */
footer {
  text-align: center;
  padding: 20px 0;
  color: #999;
  font-size: 0.8rem;
}