:root {
  /* Цветовая палитра ВКонтакте + Эко-стиль */
  --vk-blue: #0077FF;
  --vk-blue-hover: #0066DD;
  --bg-gradient-start: #f8f9fa;
  --bg-gradient-end: #e2e8f0;
  --card-bg: rgba(255, 255, 255, 0.9);
  --text-main: #000000;
  --text-secondary: #6B7280;
  --border-color: #E5E7EB;
  --success-color: #10B981;
  --option-hover: #F3F4F6;
  --option-selected-bg: #EBF5FF;
  --option-selected-border: #0077FF;
  
  --radius-lg: 16px;
  --radius-md: 12px;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  background: linear-gradient(135deg, var(--bg-gradient-start) 0%, var(--bg-gradient-end) 100%);
  color: var(--text-main);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  -webkit-font-smoothing: antialiased;
}

.app-container {
  width: 100%;
  max-width: 600px;
  min-height: 100vh;
  padding: 20px;
  position: relative;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

/* Экраны */
.screen {
  display: none;
  width: 100%;
  animation: fadeIn 0.4s ease-out;
}

.screen.active {
  display: flex;
  flex-direction: column;
}

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

/* Карточки (Glassmorphism) */
.glass-effect {
  background: var(--card-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.5);
}

.card {
  border-radius: var(--radius-lg);
  padding: 30px;
  box-shadow: var(--shadow-lg);
  text-align: center;
}

.quiz-card {
  text-align: left;
  margin-top: 20px;
}

/* Типографика */
.main-title {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 12px;
  line-height: 1.3;
}

.subtitle {
  font-size: 15px;
  color: var(--text-secondary);
  margin-bottom: 24px;
  line-height: 1.5;
}

.question-title {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 20px;
  line-height: 1.4;
}

/* Кнопки */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 15px;
  cursor: pointer;
  transition: all 0.2s ease;
  border: none;
  outline: none;
  font-family: inherit;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-primary {
  background-color: var(--vk-blue);
  color: white;
}

.btn-primary:hover:not(:disabled) {
  background-color: var(--vk-blue-hover);
}

.btn-secondary {
  background-color: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--option-hover);
  color: var(--text-main);
}

.btn-large {
  width: 100%;
  padding: 16px;
  font-size: 16px;
}

/* Прогресс-бар */
.progress-container {
  margin-bottom: 24px;
  width: 100%;
}

.progress-text {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 8px;
  text-align: right;
}

.progress-bar-bg {
  height: 6px;
  background-color: var(--border-color);
  border-radius: 3px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background-color: var(--vk-blue);
  width: 0%;
  transition: width 0.3s ease;
  border-radius: 3px;
}

/* Варианты ответов */
.options-container {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 30px;
}

.option-btn {
  display: flex;
  align-items: center;
  width: 100%;
  padding: 16px;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  background-color: white;
  color: var(--text-main);
  font-size: 16px;
  font-weight: 500;
  text-align: left;
  cursor: pointer;
  transition: all 0.2s ease;
}

.option-btn:hover {
  border-color: #cbd5e1;
  background-color: var(--option-hover);
}

.option-btn.selected {
  border-color: var(--option-selected-border);
  background-color: var(--option-selected-bg);
}

/* Для множественного выбора */
.checkbox-icon {
  width: 20px;
  height: 20px;
  border: 2px solid var(--border-color);
  border-radius: 4px;
  margin-right: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}

.option-btn.selected .checkbox-icon {
  background-color: var(--vk-blue);
  border-color: var(--vk-blue);
}

.option-btn.selected .checkbox-icon::after {
  content: '';
  width: 5px;
  height: 10px;
  border: solid white;
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
  margin-top: -2px;
}

/* Навигация квиза */
.quiz-footer {
  display: flex;
  justify-content: space-between;
  gap: 12px;
}

.quiz-footer button {
  flex: 1;
}

/* Экран завершения */
.icon-success {
  font-size: 48px;
  margin-bottom: 16px;
}

.permission-box {
  background-color: #f8fafc;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px;
  margin-top: 24px;
}

.permission-box p {
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.success-message {
  margin-top: 20px;
  padding: 16px;
  background-color: #ecfdf5;
  color: #065f46;
  border-radius: var(--radius-md);
  font-weight: 500;
}

/* Загрузчик */
.loader {
  border: 4px solid rgba(0, 119, 255, 0.2);
  border-left-color: var(--vk-blue);
  border-radius: 50%;
  width: 40px;
  height: 40px;
  animation: spin 1s linear infinite;
  margin: 0 auto 16px auto;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

#screen-loading p {
  text-align: center;
  color: var(--text-secondary);
  font-weight: 500;
}

/* Адаптивность для мобильных устройств VK */
@media (max-width: 480px) {
  .app-container {
    padding: 12px;
    height: 100vh;
    justify-content: flex-start;
  }
  
  .card {
    padding: 20px;
    box-shadow: none;
    border: none;
    background: transparent;
  }
  
  .glass-effect {
    backdrop-filter: none;
    -webkit-backdrop-filter: none;
  }
  
  .quiz-card {
    margin-top: 0;
  }
  
  .option-btn {
    padding: 14px;
    font-size: 15px;
  }
}