/* ===== RESET & BASE ===== */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

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

:root {
  --color-bg: #f0f2f5;
  --color-surface: #ffffff;
  --color-primary: #1a1f35;
  --color-accent: #0066ff;
  --color-accent-hover: #0052cc;
  --color-accent-light: rgba(0, 102, 255, 0.08);
  --color-success: #00c853;
  --color-success-hover: #00a844;
  --color-error: #ff3d00;
  --color-error-hover: #dd3400;
  --color-text: #1a1f35;
  --color-text-secondary: #6b7280;
  --color-border: #e5e7eb;
  --color-progress-bg: #e5e7eb;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 2px 8px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.1);
  --shadow-xl: 0 12px 40px rgba(0,0,0,0.12);
  --radius: 8px;
  --radius-lg: 12px;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --transition: 0.2s ease;
}

[data-theme="dark"] {
  --color-bg: #0f1117;
  --color-surface: #1a1d27;
  --color-primary: #ffffff;
  --color-accent-light: rgba(0, 102, 255, 0.15);
  --color-text: #f0f0f0;
  --color-text-secondary: #9ca3af;
  --color-border: #2a2d3a;
  --color-progress-bg: #2a2d3a;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.2);
  --shadow-md: 0 2px 8px rgba(0,0,0,0.3);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.4);
  --shadow-xl: 0 12px 40px rgba(0,0,0,0.5);
}

body {
  font-family: var(--font);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
}

/* ===== HEADER / NAV ===== */
.navbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.navbar__title {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: -0.3px;
}

.navbar__actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.navbar__toggle {
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 8px 10px;
  cursor: pointer;
  color: var(--color-text);
  font-size: 18px;
  transition: background var(--transition), border-color var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
}

.navbar__toggle:hover {
  background: var(--color-accent-light);
  border-color: var(--color-accent);
}

.navbar__back {
  display: flex;
  align-items: center;
  gap: 6px;
  background: none;
  border: none;
  color: var(--color-accent);
  font-size: 14px;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  padding: 8px 0;
}

.navbar__back:hover {
  opacity: 0.8;
}

/* ===== CONTAINER ===== */
.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 40px 24px;
}

/* ===== HOME HERO ===== */
.home-hero {
  text-align: center;
  margin-bottom: 48px;
}

.home-hero__label {
  display: inline-block;
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--color-accent);
  background: var(--color-accent-light);
  padding: 6px 14px;
  border-radius: 20px;
  margin-bottom: 16px;
}

.home-hero__title {
  font-size: 28px;
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.5px;
  margin-bottom: 8px;
}

.home-hero__subtitle {
  font-size: 15px;
  color: var(--color-text-secondary);
  font-weight: 400;
}

.home-hero__shortcut {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 12px;
  color: var(--color-text-secondary);
}

/* ===== CHAPTER CARDS ===== */
.chapter-grid {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.chapter-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: box-shadow var(--transition), border-color var(--transition);
}

.chapter-card:hover {
  box-shadow: var(--shadow-lg);
  border-color: var(--color-accent);
}

.chapter-card__main {
  display: flex;
  align-items: center;
  gap: 24px;
  padding: 24px 28px;
  cursor: pointer;
}

.chapter-card__icon {
  width: 72px;
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-accent-light);
  border-radius: var(--radius-lg);
  flex-shrink: 0;
  color: var(--color-accent);
}

.chapter-card__body {
  flex: 1;
  min-width: 0;
}

.chapter-card__name {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--color-accent);
  margin-bottom: 4px;
}

.chapter-card__title {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 4px;
  letter-spacing: -0.2px;
}

.chapter-card__desc {
  font-size: 13px;
  color: var(--color-text-secondary);
  margin-bottom: 12px;
}

.chapter-card__meta {
  display: flex;
  align-items: center;
  gap: 16px;
}

.chapter-card__count {
  font-size: 13px;
  color: var(--color-text-secondary);
  font-weight: 500;
}

.chapter-card__progress-bar {
  flex: 1;
  height: 4px;
  background: var(--color-progress-bg);
  border-radius: 2px;
  overflow: hidden;
  max-width: 180px;
}

.chapter-card__progress-fill {
  height: 100%;
  background: var(--color-accent);
  border-radius: 2px;
  transition: width 0.4s ease;
}

.chapter-card__arrow {
  color: var(--color-text-secondary);
  flex-shrink: 0;
  transition: transform var(--transition), color var(--transition);
}

.chapter-card__main:hover .chapter-card__arrow {
  transform: translateX(4px);
  color: var(--color-accent);
}

/* Chapter card actions bar */
.chapter-card__actions {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 28px 16px;
}

.chapter-card__action-btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 12px;
  font-weight: 600;
  font-family: var(--font);
  padding: 6px 12px;
  border-radius: 6px;
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.chapter-card__action-btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  background: var(--color-accent-light);
}

.chapter-card__action-btn--mistakes {
  color: var(--color-error);
  border-color: rgba(255, 61, 0, 0.2);
  background: rgba(255, 61, 0, 0.05);
}

.chapter-card__action-btn--mistakes:hover {
  border-color: var(--color-error);
  color: var(--color-error);
  background: rgba(255, 61, 0, 0.1);
}

.chapter-card__action-btn--reset {
  margin-left: auto;
  color: var(--color-text-secondary);
}

.chapter-card__action-btn--reset:hover {
  color: var(--color-error);
  border-color: var(--color-error);
  background: rgba(255, 61, 0, 0.05);
}

/* ===== RANDOM MODE BUTTON ===== */
.random-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  width: 100%;
  margin-top: 24px;
  padding: 16px 24px;
  background: var(--color-surface);
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-lg);
  font-size: 15px;
  font-weight: 600;
  font-family: var(--font);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.random-btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
  background: var(--color-accent-light);
}

/* ===== LEARN MODE HEADER ===== */
.learn-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.learn-header__title {
  font-size: 15px;
  font-weight: 600;
  color: var(--color-text);
}

.learn-header__counter {
  font-size: 14px;
  font-weight: 700;
  color: var(--color-accent);
  background: var(--color-accent-light);
  padding: 4px 14px;
  border-radius: 20px;
}

.learn-header__close {
  background: none;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--color-text);
  transition: background var(--transition), border-color var(--transition);
  font-family: var(--font);
}

.learn-header__close:hover {
  background: var(--color-accent-light);
  border-color: var(--color-accent);
}

/* ===== FLASHCARD ===== */
.flashcard-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 48px 24px 32px;
  min-height: calc(100vh - 140px);
}

.flashcard-wrapper {
  perspective: 1200px;
  width: 100%;
  max-width: 520px;
  height: 360px;
  margin-bottom: 36px;
}

.flashcard {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
}

.flashcard--flipped {
  transform: rotateY(180deg);
}

.flashcard__face {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 32px;
}

.flashcard__face--front {
  flex-direction: column;
  gap: 16px;
}

.flashcard__face--back {
  transform: rotateY(180deg);
  flex-direction: column;
  gap: 16px;
  align-items: flex-start;
  justify-content: center;
}

.flashcard__word {
  font-size: 32px;
  font-weight: 800;
  color: var(--color-text);
  text-align: center;
  line-height: 1.25;
  letter-spacing: -0.3px;
}

.flashcard__hint {
  font-size: 13px;
  color: var(--color-text-secondary);
  text-align: center;
  display: flex;
  align-items: center;
  gap: 6px;
}

.flashcard__hint::before {
  content: '';
  display: inline-block;
  width: 16px;
  height: 16px;
  border: 2px solid var(--color-text-secondary);
  border-radius: 50%;
}

.flashcard__translation {
  font-size: 26px;
  font-weight: 700;
  color: var(--color-accent);
  width: 100%;
  letter-spacing: -0.2px;
}

.flashcard__example {
  font-size: 14px;
  color: var(--color-text-secondary);
  font-style: italic;
  line-height: 1.6;
  width: 100%;
  padding: 12px 16px;
  background: var(--color-bg);
  border-radius: var(--radius);
  border-left: 3px solid var(--color-accent);
}

.flashcard__grammar {
  font-size: 12px;
  color: var(--color-accent);
  background: var(--color-accent-light);
  padding: 5px 12px;
  border-radius: 20px;
  font-weight: 600;
  letter-spacing: 0.2px;
}

/* ===== ASSESSMENT BUTTONS ===== */
.assessment-buttons {
  display: flex;
  gap: 16px;
  width: 100%;
  max-width: 520px;
}

.assessment-btn {
  flex: 1;
  height: 60px;
  border: none;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: background var(--transition), transform 0.1s ease, opacity var(--transition), box-shadow var(--transition);
  position: relative;
}

.assessment-btn:active {
  transform: scale(0.98);
}

.assessment-btn--wrong {
  background: var(--color-error);
  color: #ffffff;
}

.assessment-btn--wrong:hover {
  background: var(--color-error-hover);
  box-shadow: 0 4px 16px rgba(255, 61, 0, 0.3);
}

.assessment-btn--correct {
  background: var(--color-success);
  color: #ffffff;
}

.assessment-btn--correct:hover {
  background: var(--color-success-hover);
  box-shadow: 0 4px 16px rgba(0, 200, 83, 0.3);
}

.assessment-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.assessment-btn__icon {
  font-size: 20px;
  font-weight: 700;
}

.assessment-btn__shortcut {
  position: absolute;
  right: 12px;
  font-size: 11px;
  opacity: 0.6;
  font-weight: 500;
  background: rgba(255,255,255,0.15);
  padding: 2px 6px;
  border-radius: 4px;
}

/* ===== TYPING MODE ===== */
.typing-card {
  width: 100%;
  max-width: 520px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
}

.typing-card__prompt {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  padding: 40px 32px;
  width: 100%;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.typing-card__word {
  font-size: 28px;
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.3px;
}

.typing-card__form {
  width: 100%;
  display: flex;
  gap: 10px;
}

.typing-card__input {
  flex: 1;
  padding: 14px 18px;
  font-size: 16px;
  font-family: var(--font);
  font-weight: 500;
  border: 2px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-surface);
  color: var(--color-text);
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.typing-card__input:focus {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-light);
}

.typing-card__input--correct {
  border-color: var(--color-success) !important;
  box-shadow: 0 0 0 3px rgba(0, 200, 83, 0.15) !important;
}

.typing-card__input--almost {
  border-color: #ff9800 !important;
  box-shadow: 0 0 0 3px rgba(255, 152, 0, 0.15) !important;
}

.typing-card__input--wrong {
  border-color: var(--color-error) !important;
  box-shadow: 0 0 0 3px rgba(255, 61, 0, 0.15) !important;
}

.typing-card__submit {
  padding: 14px 24px;
  font-size: 15px;
  font-weight: 600;
  font-family: var(--font);
  border: none;
  border-radius: var(--radius);
  background: var(--color-accent);
  color: #ffffff;
  cursor: pointer;
  transition: background var(--transition), transform 0.1s ease;
  white-space: nowrap;
}

.typing-card__submit:hover {
  background: var(--color-accent-hover);
}

.typing-card__submit:active {
  transform: scale(0.98);
}

.typing-card__submit:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.typing-card__feedback {
  width: 100%;
  padding: 14px 18px;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 10px;
}

.typing-card__feedback--correct {
  background: rgba(0, 200, 83, 0.1);
  color: var(--color-success);
  border: 1px solid rgba(0, 200, 83, 0.3);
}

.typing-card__feedback--almost {
  background: rgba(255, 152, 0, 0.1);
  color: #e68900;
  border: 1px solid rgba(255, 152, 0, 0.3);
}

.typing-card__feedback--wrong {
  background: rgba(255, 61, 0, 0.1);
  color: var(--color-error);
  border: 1px solid rgba(255, 61, 0, 0.3);
}

.typing-card__feedback-icon {
  font-size: 18px;
  font-weight: 700;
}

.typing-card__feedback strong {
  font-weight: 700;
}

/* ===== RESULT SCREEN ===== */
.result {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: calc(100vh - 120px);
  padding: 48px 24px;
  text-align: center;
}

.result__icon {
  margin-bottom: 24px;
  color: var(--color-accent);
}

.result__title {
  font-size: 26px;
  font-weight: 800;
  color: var(--color-text);
  margin-bottom: 8px;
  letter-spacing: -0.3px;
}

.result__subtitle {
  font-size: 15px;
  color: var(--color-text-secondary);
  margin-bottom: 40px;
}

.result__score {
  font-size: 52px;
  font-weight: 800;
  color: var(--color-accent);
  margin-bottom: 8px;
  letter-spacing: -1px;
}

.result__score-label {
  font-size: 14px;
  color: var(--color-text-secondary);
  margin-bottom: 40px;
}

.result__btn {
  background: var(--color-primary);
  color: #ffffff;
  border: none;
  border-radius: var(--radius);
  padding: 14px 32px;
  font-size: 15px;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  transition: background var(--transition), transform 0.1s ease, box-shadow var(--transition);
}

[data-theme="dark"] .result__btn {
  background: var(--color-accent);
}

.result__btn:hover {
  background: #2d3250;
  box-shadow: var(--shadow-lg);
}

[data-theme="dark"] .result__btn:hover {
  background: var(--color-accent-hover);
}

.result__btn:active {
  transform: scale(0.98);
}

/* ===== STATISTICS PAGE ===== */
.stats-header {
  margin-bottom: 32px;
}

.stats-header__title {
  font-size: 24px;
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.3px;
  margin-bottom: 20px;
}

.stats-overview {
  display: flex;
  gap: 16px;
}

.stats-overview__item {
  flex: 1;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 20px;
  text-align: center;
}

.stats-overview__value {
  font-size: 32px;
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.5px;
  margin-bottom: 4px;
}

.stats-overview__value--correct {
  color: var(--color-success);
}

.stats-overview__value--wrong {
  color: var(--color-error);
}

.stats-overview__label {
  font-size: 13px;
  color: var(--color-text-secondary);
  font-weight: 500;
}

.stats-table {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.stats-table__header {
  display: grid;
  grid-template-columns: 1fr 1fr 50px 50px;
  gap: 8px;
  padding: 12px 20px;
  background: var(--color-bg);
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--color-text-secondary);
  border-bottom: 1px solid var(--color-border);
}

.stats-table__row {
  display: grid;
  grid-template-columns: 1fr 1fr 50px 50px;
  gap: 8px;
  padding: 12px 20px;
  font-size: 14px;
  border-bottom: 1px solid var(--color-border);
  transition: background var(--transition);
}

.stats-table__row:last-child {
  border-bottom: none;
}

.stats-table__row:hover {
  background: var(--color-bg);
}

.stats-table__word {
  font-weight: 600;
  color: var(--color-text);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.stats-table__trans {
  color: var(--color-text-secondary);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.stats-table__num {
  text-align: center;
  font-weight: 600;
}

.stats-table__num--correct {
  color: var(--color-success);
}

.stats-table__num--wrong {
  color: var(--color-error);
}

.stats-empty {
  text-align: center;
  padding: 60px 24px;
  color: var(--color-text-secondary);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  .container {
    padding: 28px 16px;
  }

  .home-hero {
    margin-bottom: 32px;
  }

  .home-hero__title {
    font-size: 22px;
  }

  .chapter-card__main {
    padding: 20px;
    gap: 16px;
  }

  .chapter-card__icon {
    width: 56px;
    height: 56px;
    border-radius: var(--radius);
  }

  .chapter-card__title {
    font-size: 16px;
  }

  .chapter-card__progress-bar {
    max-width: 120px;
  }

  .chapter-card__actions {
    padding: 0 20px 14px;
    flex-wrap: wrap;
  }

  .flashcard-wrapper {
    max-width: 90vw;
    height: 320px;
  }

  .flashcard__word {
    font-size: 24px;
  }

  .flashcard__translation {
    font-size: 20px;
  }

  .flashcard__example {
    font-size: 13px;
  }

  .assessment-buttons {
    flex-direction: column;
    max-width: 90vw;
  }

  .assessment-btn {
    height: 56px;
  }

  .assessment-btn__shortcut {
    display: none;
  }

  .typing-card {
    max-width: 90vw;
  }

  .typing-card__word {
    font-size: 22px;
  }

  .typing-card__form {
    flex-direction: column;
  }

  .stats-overview {
    flex-direction: column;
    gap: 10px;
  }

  .stats-table__header,
  .stats-table__row {
    grid-template-columns: 1fr 45px 45px;
    font-size: 13px;
  }

  .stats-table__trans {
    display: none;
  }

  .result__score {
    font-size: 40px;
  }
}

/* ===== ANIMATIONS ===== */
.fade-in {
  animation: fadeIn 0.35s ease;
}

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