:root {
  --font-sans: "Geist", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: "Geist Mono", ui-monospace, SFMono-Regular, Menlo, Monaco, monospace;
  --font-kanji: "Geist", "Noto Sans CJK JP", "Hiragino Sans", "Meiryo", "Yu Gothic", sans-serif;

  --bg-canvas: #f8fafc;
  --bg-card: #ffffff;
  --bg-card-subtle: #f1f5f9;
  --bg-card-hover: #e2e8f0;
  --border-subtle: #e2e8f0;
  --border-strong: #cbd5e1;

  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-dim: #94a3b8;

  --vibrant-primary: #6366f1;       
  --vibrant-primary-hover: #4f46e5;
  --vibrant-primary-light: #eef2ff;
  --vibrant-accent: #06b6d4;       
  --vibrant-success: #10b981;      
  --vibrant-success-bg: #ecfdf5;
  --vibrant-danger: #f43f5e;        
  --vibrant-danger-bg: #fff1f2;
  --vibrant-warning: #f59e0b;      
  --vibrant-warning-bg: #fffbeb;

  --shadow-sm: 0 2px 8px -2px rgba(99, 102, 241, 0.06), 0 1px 4px -1px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 10px 25px -5px rgba(99, 102, 241, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.03);
  --shadow-lg: 0 20px 35px -10px rgba(99, 102, 241, 0.12), 0 10px 15px -5px rgba(0, 0, 0, 0.04);

  --radius-pill: 9999px;
  --radius-xl: 26px;
  --radius-lg: 20px;
  --radius-md: 16px;
  --radius-sm: 12px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg-canvas: #09090b;
    --bg-card: #121217;
    --bg-card-subtle: #1c1c24;
    --bg-card-hover: #262633;
    --border-subtle: #272732;
    --border-strong: #3f3f50;

    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --text-dim: #64748b;

    --vibrant-primary: #818cf8;
    --vibrant-primary-hover: #a5b4fc;
    --vibrant-primary-light: rgba(99, 102, 241, 0.18);
    --vibrant-accent: #22d3ee;
    --vibrant-success: #34d399;
    --vibrant-success-bg: rgba(16, 185, 129, 0.15);
    --vibrant-danger: #fb7185;
    --vibrant-danger-bg: rgba(244, 63, 94, 0.15);
    --vibrant-warning: #fbbf24;
    --vibrant-warning-bg: rgba(245, 158, 11, 0.15);

    --shadow-sm: 0 2px 8px -2px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 12px 28px -6px rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 20px 40px -10px rgba(0, 0, 0, 0.6);
  }
}

[data-theme="dark"] {
  --bg-canvas: #09090b;
  --bg-card: #121217;
  --bg-card-subtle: #1c1c24;
  --bg-card-hover: #262633;
  --border-subtle: #272732;
  --border-strong: #3f3f50;

  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;

  --vibrant-primary: #818cf8;
  --vibrant-primary-hover: #a5b4fc;
  --vibrant-primary-light: rgba(99, 102, 241, 0.18);
  --vibrant-accent: #22d3ee;
  --vibrant-success: #34d399;
  --vibrant-success-bg: rgba(16, 185, 129, 0.15);
  --vibrant-danger: #fb7185;
  --vibrant-danger-bg: rgba(244, 63, 94, 0.15);
  --vibrant-warning: #fbbf24;
  --vibrant-warning-bg: rgba(245, 158, 11, 0.15);

  --shadow-sm: 0 2px 8px -2px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 12px 28px -6px rgba(0, 0, 0, 0.5);
  --shadow-lg: 0 20px 40px -10px rgba(0, 0, 0, 0.6);
}

[data-theme="light"] {
  --bg-canvas: #f8fafc;
  --bg-card: #ffffff;
  --bg-card-subtle: #f1f5f9;
  --bg-card-hover: #e2e8f0;
  --border-subtle: #e2e8f0;
  --border-strong: #cbd5e1;

  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-dim: #94a3b8;

  --vibrant-primary: #6366f1;
  --vibrant-primary-hover: #4f46e5;
  --vibrant-primary-light: #eef2ff;
  --vibrant-accent: #06b6d4;
  --vibrant-success: #10b981;
  --vibrant-success-bg: #ecfdf5;
  --vibrant-danger: #f43f5e;
  --vibrant-danger-bg: #fff1f2;
  --vibrant-warning: #f59e0b;
  --vibrant-warning-bg: #fffbeb;

  --shadow-sm: 0 2px 8px -2px rgba(99, 102, 241, 0.06), 0 1px 4px -1px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 10px 25px -5px rgba(99, 102, 241, 0.08), 0 8px 10px -6px rgba(0, 0, 0, 0.03);
  --shadow-lg: 0 20px 35px -10px rgba(99, 102, 241, 0.12), 0 10px 15px -5px rgba(0, 0, 0, 0.04);
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-canvas);
  color: var(--text-main);
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 20px 14px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color 0.2s ease, color 0.2s ease;
}

#app {
  display: flex;
  flex-direction: column;
  min-height: calc(100vh - 40px);
  max-width: 920px;
  margin: 0 auto;
  width: 100%;
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  transition: background-color 0.2s ease, border-color 0.2s ease, box-shadow 0.2s ease;
}

.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 24px;
  background-color: var(--bg-card);
  border-bottom: 1px solid var(--border-subtle);
  flex-wrap: wrap;
  gap: 14px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 12px;
}

.app-title {
  font-size: 1.45rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  cursor: pointer;
  user-select: none;
  background: linear-gradient(135deg, var(--vibrant-primary), var(--vibrant-primary-hover));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
  display: inline-block;
}

.app-title span {
  font-size: 0.95rem;
  font-weight: 600;
  margin-left: 6px;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

.header-right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.quick-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.github-icon {
  position: relative;
  top: 3px;
}

.nav-btn,
.footer-nav-btn {
  font-family: var(--font-sans);
  font-size: 0.88rem;
  font-weight: 600;
  padding: 7px 16px;
  border-radius: var(--radius-pill);
  border: 1px solid transparent;
  background-color: var(--bg-card-subtle);
  color: var(--text-muted);
  cursor: pointer;
  transition: background 0.18s ease, color 0.18s ease, border-color 0.18s ease, box-shadow 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.15s cubic-bezier(0.16, 1, 0.3, 1);
  user-select: none;
  will-change: transform;
}

.nav-btn:hover,
.footer-nav-btn:hover {
  background-color: var(--vibrant-primary-light);
  color: var(--vibrant-primary);
  border-color: rgba(99, 102, 241, 0.2);
  transform: translateY(-0.5px);
}

.nav-btn:active,
.footer-nav-btn:active {
  transform: scale(0.975);
}

.nav-btn.active,
.footer-nav-btn.active {
  background: linear-gradient(135deg, var(--vibrant-primary), var(--vibrant-primary-hover));
  color: #ffffff;
  box-shadow: 0 3px 12px rgba(99, 102, 241, 0.32);
  transform: none;
}

@keyframes screenFadeIn {
  from {
    opacity: 0;
    transform: translateY(5px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes phaseFadeIn {
  from {
    opacity: 0;
    transform: translateY(4px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes bannerPop {
  0% {
    opacity: 0;
    transform: scale(0.97);
  }
  100% {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes contentFadeIn {
  from {
    opacity: 0.4;
    transform: translateY(3px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes glyphFadeIn {
  from {
    opacity: 0.35;
    transform: scale(0.975);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.content-fade {
  animation: contentFadeIn 0.18s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

.glyph-fade {
  animation: glyphFadeIn 0.18s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

/* main content */
.app-content {
  flex: 1;
  padding: 32px 28px;
  display: flex;
  flex-direction: column;
}

.screen {
  display: none;
  flex-direction: column;
  flex: 1;
}

.screen.active {
  display: flex;
  animation: screenFadeIn 0.22s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

.btn {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  padding: 11px 22px;
  border-radius: var(--radius-pill);
  cursor: pointer;
  font-weight: 600;
  border: 1px solid transparent;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 46px;
  text-decoration: none;
  user-select: none;
  transition: background 0.18s ease, border-color 0.18s ease, color 0.18s ease, box-shadow 0.2s cubic-bezier(0.16, 1, 0.3, 1), transform 0.15s cubic-bezier(0.16, 1, 0.3, 1);
  will-change: transform;
}

.btn:active {
  transform: scale(0.985) translateY(0.5px);
}

.btn-primary {
  background: linear-gradient(135deg, var(--vibrant-primary), var(--vibrant-primary-hover));
  color: #ffffff;
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
}

.btn-primary:hover {
  box-shadow: 0 6px 18px rgba(99, 102, 241, 0.45);
  filter: brightness(1.05);
}

.btn-secondary {
  background-color: var(--bg-card-subtle);
  color: var(--text-main);
  border: 1px solid var(--border-subtle);
}

.btn-secondary:hover {
  background-color: var(--bg-card-hover);
  border-color: var(--border-strong);
}

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

.btn-outline:hover {
  background-color: var(--bg-card-subtle);
  color: var(--text-main);
}

.btn-danger {
  background: linear-gradient(135deg, var(--vibrant-danger), #e11d48);
  color: #ffffff;
  box-shadow: 0 4px 14px rgba(244, 63, 94, 0.35);
}

.btn-danger:hover {
  filter: brightness(1.08);
}

.btn-large {
  font-size: 1.05rem;
  padding: 14px 28px;
  border-radius: var(--radius-pill);
}

.key-hint {
  font-family: var(--font-mono);
  font-size: 0.78em;
  padding: 3px 8px;
  background-color: rgba(0, 0, 0, 0.06);
  border-radius: var(--radius-pill);
  font-weight: 600;
  display: inline-flex;
  align-items: center;
}

@media (prefers-color-scheme: dark) {
  .key-hint {
    background-color: rgba(255, 255, 255, 0.12);
  }
}

/* menu */
.menu-container {
  display: flex;
  flex-direction: column;
  max-width: 580px;
  margin: auto;
  width: 100%;
  gap: 22px;
}

.menu-header h2 {
  font-size: 1.75rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 6px;
}

.subtitle {
  color: var(--text-muted);
  font-size: 0.95rem;
}

.menu-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.menu-item {
  display: grid;
  grid-template-columns: 48px 1fr auto;
  align-items: center;
  padding: 16px 20px;
  background-color: var(--bg-card);
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  text-align: left;
  cursor: pointer;
  color: var(--text-main);
  box-shadow: var(--shadow-sm);
  transition: border-color 0.18s ease, background-color 0.18s ease, transform 0.18s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.18s cubic-bezier(0.16, 1, 0.3, 1);
  will-change: transform;
}

.menu-item .key-hint {
  width: 30px;
  height: 30px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-pill);
  font-size: 0.95rem;
  font-weight: 700;
  padding: 0;
  transition: background-color 0.18s ease, color 0.18s ease;
}

.menu-item .menu-label {
  font-size: 1.15rem;
  font-weight: 700;
}

.menu-item .menu-desc {
  grid-column: 2 / -1;
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.menu-item:hover,
.menu-item.active {
  border-color: var(--vibrant-primary);
  background-color: var(--vibrant-primary-light);
  transform: translateY(-1.5px);
  box-shadow: var(--shadow-md);
}

.menu-item:active {
  transform: scale(0.992) translateY(0);
}

/* study screen */
.study-container {
  display: flex;
  flex-direction: column;
  gap: 24px;
  max-width: 780px;
  margin: 0 auto;
  width: 100%;
}

.study-nav-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.study-counter {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-muted);
  background-color: var(--bg-card-subtle);
  padding: 6px 14px;
  border-radius: var(--radius-pill);
}

.card-display {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 36px 30px;
  text-align: center;
  box-shadow: var(--shadow-md);
}

.kanji-glyph {
  font-family: var(--font-kanji);
  font-size: 6.5rem;
  font-weight: 600;
  line-height: 1.1;
  margin-bottom: 12px;
  color: var(--text-main);
  text-shadow: 0 4px 16px rgba(99, 102, 241, 0.1);
}

.kanji-meaning {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 26px;
  color: var(--vibrant-primary);
}

.readings-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 14px;
  margin-bottom: 32px;
  text-align: left;
}

.reading-box {
  background-color: var(--bg-card-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  transition: border-color 0.2s;
}

.reading-box:hover {
  border-color: var(--border-strong);
}

.reading-label {
  display: block;
  font-size: 0.76rem;
  text-transform: uppercase;
  color: var(--text-dim);
  font-weight: 700;
  letter-spacing: 0.05em;
  margin-bottom: 4px;
}

.reading-value {
  font-size: 1.1rem;
  font-weight: 600;
}

.vocabulary-section {
  text-align: left;
  border-top: 1px solid var(--border-subtle);
  padding-top: 24px;
}

.vocabulary-section h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 14px;
  color: var(--text-muted);
}

.vocab-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.vocab-item {
  background-color: var(--bg-card-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 14px 18px;
  transition: border-color 0.18s ease, background-color 0.18s ease, box-shadow 0.18s ease;
}

.vocab-item:hover {
  border-color: var(--border-strong);
  background-color: var(--bg-card);
  box-shadow: var(--shadow-sm);
}

.vocab-header {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 4px;
}

.vocab-word {
  font-family: var(--font-kanji);
  font-size: 1.3rem;
  font-weight: 700;
}

.vocab-reading {
  color: var(--vibrant-primary);
  font-size: 0.95rem;
  font-weight: 500;
}

.vocab-meaning {
  font-size: 0.95rem;
  color: var(--text-main);
  font-weight: 500;
}

.vocab-examples {
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px dashed var(--border-subtle);
  font-size: 0.88rem;
}

.vocab-example-ja {
  color: var(--text-muted);
}

.vocab-example-en {
  color: var(--text-dim);
  font-style: italic;
}

.empty-hint {
  color: var(--text-muted);
  font-size: 0.95rem;
  font-style: italic;
}

.study-bottom-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

/* quiz screen */
.quiz-container {
  display: flex;
  flex-direction: column;
  max-width: 660px;
  margin: auto;
  width: 100%;
}

.quiz-phase {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 36px 30px;
  width: 100%;
  box-shadow: var(--shadow-md);
}

.quiz-phase:not(.hidden) {
  animation: phaseFadeIn 0.2s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

.quiz-phase.hidden {
  display: none;
}

.quiz-status-bar {
  display: flex;
  justify-content: space-between;
  width: 100%;
  margin-bottom: 24px;
  font-size: 0.88rem;
  color: var(--text-muted);
}

.quiz-mode-tag {
  background-color: var(--vibrant-primary-light);
  color: var(--vibrant-primary);
  padding: 4px 12px;
  border-radius: var(--radius-pill);
  font-weight: 700;
  font-size: 0.8rem;
}

.quiz-progress-tag {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  background-color: var(--bg-card-subtle);
  padding: 4px 12px;
  border-radius: var(--radius-pill);
}

.quiz-kanji-glyph {
  font-family: var(--font-kanji);
  font-size: 7.5rem;
  font-weight: 600;
  line-height: 1;
  margin: 12px 0 18px;
  color: var(--text-main);
  text-shadow: 0 4px 20px rgba(99, 102, 241, 0.12);
}

.quiz-prompt {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 26px;
}

#quiz-form {
  width: 100%;
  max-width: 480px;
}

.quiz-input-group {
  display: flex;
  gap: 12px;
  width: 100%;
  flex-direction: column;
}

.quiz-input {
  font-family: var(--font-sans);
  font-size: 1.25rem;
  font-weight: 500;
  padding: 16px 24px;
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-pill);
  background-color: var(--bg-card-subtle);
  color: var(--text-main);
  text-align: center;
  outline: none;
  min-height: 56px;
  transition: border-color 0.18s ease, background-color 0.18s ease, box-shadow 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.quiz-input:focus {
  border-color: var(--vibrant-primary);
  background-color: var(--bg-card);
  box-shadow: 0 0 0 4px var(--vibrant-primary-light);
}

.btn-submit {
  min-height: 50px;
  font-size: 1.05rem;
  border-radius: var(--radius-pill);
}

.quiz-controls-bottom {
  margin-top: 28px;
}

/* result and rating */
.result-banner {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 12px 28px;
  border-radius: var(--radius-pill);
  font-size: 1.3rem;
  font-weight: 800;
  margin-bottom: 24px;
  width: auto;
  box-shadow: var(--shadow-sm);
  animation: bannerPop 0.22s cubic-bezier(0.16, 1, 0.3, 1) forwards;
}

.result-banner.correct {
  background-color: var(--vibrant-success-bg);
  color: var(--vibrant-success);
  border: 1px solid var(--vibrant-success);
}

.result-banner.incorrect {
  background-color: var(--vibrant-danger-bg);
  color: var(--vibrant-danger);
  border: 1px solid var(--vibrant-danger);
}

.result-kanji-header {
  margin-bottom: 20px;
}

.result-glyph {
  font-family: var(--font-kanji);
  font-size: 5rem;
  font-weight: 600;
  display: block;
}

.result-readings {
  color: var(--text-muted);
  font-size: 1.05rem;
  margin-top: 4px;
  font-weight: 500;
}

.result-comparison {
  width: 100%;
  max-width: 520px;
  background-color: var(--bg-card-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 18px 22px;
  margin-bottom: 28px;
  text-align: left;
}

.comparison-row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px dashed var(--border-subtle);
  font-size: 1rem;
}

.comparison-row:last-child {
  border-bottom: none;
}

.comparison-label {
  color: var(--text-muted);
  font-weight: 600;
}

.comparison-value.user-val {
  font-weight: 600;
}

.comparison-value.correct-val {
  font-weight: 700;
  color: var(--vibrant-primary);
}

.srs-rating-section {
  width: 100%;
}

.rating-prompt {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 16px;
}

.rating-buttons-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 12px;
  width: 100%;
}

.rating-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 14px 10px;
  border-radius: var(--radius-lg);
  border: 1.5px solid var(--border-subtle);
  background-color: var(--bg-card-subtle);
  color: var(--text-main);
  cursor: pointer;
  transition: border-color 0.18s ease, background-color 0.18s ease, transform 0.18s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.18s cubic-bezier(0.16, 1, 0.3, 1);
  min-height: 80px;
  box-shadow: var(--shadow-sm);
  will-change: transform;
}

.rating-btn:hover {
  transform: translateY(-1.5px);
  box-shadow: var(--shadow-md);
}

.rating-btn:active {
  transform: scale(0.975);
}

.rating-btn.rate-1 {
  border-color: rgba(244, 63, 94, 0.4);
}
.rating-btn.rate-1:hover {
  background-color: var(--vibrant-danger-bg);
  border-color: var(--vibrant-danger);
}

.rating-btn.rate-2 {
  border-color: rgba(245, 158, 11, 0.4);
}
.rating-btn.rate-2:hover {
  background-color: var(--vibrant-warning-bg);
  border-color: var(--vibrant-warning);
}

.rating-btn.rate-3 {
  border-color: rgba(99, 102, 241, 0.4);
}
.rating-btn.rate-3:hover {
  background-color: var(--vibrant-primary-light);
  border-color: var(--vibrant-primary);
}

.rating-btn.rate-4 {
  border-color: rgba(16, 185, 129, 0.4);
}
.rating-btn.rate-4:hover {
  background-color: var(--vibrant-success-bg);
  border-color: var(--vibrant-success);
}

.rate-num {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-muted);
}

.rate-name {
  font-size: 1.15rem;
  font-weight: 800;
  margin: 3px 0;
}

.rate-desc {
  font-size: 0.78rem;
  color: var(--text-muted);
}

.shortcut-tip {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-top: 18px;
}

/* empty state */
.empty-state {
  padding: 24px;
}

.empty-state h2 {
  font-size: 1.8rem;
  font-weight: 800;
  margin-bottom: 10px;
}

.empty-actions {
  display: flex;
  gap: 12px;
  margin-top: 26px;
  justify-content: center;
  flex-wrap: wrap;
}

/* review and stats */
.review-container {
  display: flex;
  flex-direction: column;
  gap: 26px;
  max-width: 780px;
  margin: 0 auto;
  width: 100%;
}

.section-header h2 {
  font-size: 1.75rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 4px;
}

.stats-cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 16px;
}

.stat-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 20px 18px;
  text-align: center;
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-sm);
  transition: transform 0.18s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.18s cubic-bezier(0.16, 1, 0.3, 1), border-color 0.18s ease;
  will-change: transform;
}

.stat-card:hover {
  transform: translateY(-1.5px);
  box-shadow: var(--shadow-md);
}

.stat-number {
  font-size: 2.8rem;
  font-weight: 800;
  line-height: 1.1;
  font-family: var(--font-mono);
  letter-spacing: -0.03em;
}

.stat-label {
  font-weight: 700;
  font-size: 0.95rem;
  margin: 6px 0 2px;
}

.stat-sub {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.stat-due .stat-number { color: var(--vibrant-danger); }
.stat-new .stat-number { color: var(--vibrant-primary); }
.stat-learning .stat-number { color: var(--vibrant-warning); }
.stat-total .stat-number { color: var(--text-main); }

.progress-section {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 22px;
  box-shadow: var(--shadow-sm);
}

.progress-label-row {
  display: flex;
  justify-content: space-between;
  font-weight: 700;
  font-size: 0.95rem;
  margin-bottom: 12px;
}

.progress-bar-container {
  display: flex;
  height: 18px;
  border-radius: var(--radius-pill);
  overflow: hidden;
  background-color: var(--bg-card-subtle);
  border: 1px solid var(--border-subtle);
}

.bar-segment {
  height: 100%;
  transition: width 0.85s cubic-bezier(0.16, 1, 0.3, 1);
  will-change: width;
}

.bar-due-seg {
  background: linear-gradient(90deg, var(--vibrant-danger), #e11d48);
  transition-delay: 0s;
}

.bar-learning-seg {
  background: linear-gradient(90deg, var(--vibrant-warning), #d97706);
  transition-delay: 0.08s;
}

.bar-new-seg {
  background: linear-gradient(90deg, var(--vibrant-primary), var(--vibrant-accent));
  opacity: 0.85;
  transition-delay: 0.16s;
}

.progress-legend {
  display: flex;
  gap: 20px;
  margin-top: 14px;
  font-size: 0.88rem;
  color: var(--text-muted);
  font-weight: 500;
}

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

.dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  display: inline-block;
}

.dot-due { background-color: var(--vibrant-danger); }
.dot-learning { background-color: var(--vibrant-warning); }
.dot-new { background-color: var(--vibrant-primary); }

.review-actions-panel {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
}

/* settings */
.settings-container {
  display: flex;
  flex-direction: column;
  gap: 22px;
  max-width: 680px;
  margin: 0 auto;
  width: 100%;
}

.settings-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

.settings-card h3 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 6px;
}

.setting-desc {
  font-size: 0.92rem;
  color: var(--text-muted);
  margin-bottom: 18px;
}

.level-radio-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.radio-option {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 18px;
  border: 1.5px solid var(--border-subtle);
  border-radius: var(--radius-md);
  background-color: var(--bg-card-subtle);
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 500;
  transition: border-color 0.18s ease, background-color 0.18s ease, box-shadow 0.18s ease;
}

.radio-option:hover {
  border-color: var(--vibrant-primary);
  background-color: var(--vibrant-primary-light);
}

.radio-option input[type="radio"] {
  width: 18px;
  height: 18px;
  accent-color: var(--vibrant-primary);
}

.danger-zone {
  border-color: rgba(244, 63, 94, 0.3);
  background-color: var(--vibrant-danger-bg);
}

.shortcuts-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}

.shortcuts-table td {
  padding: 10px 12px;
  border-bottom: 1px solid var(--border-subtle);
}

.shortcuts-table tr:last-child td {
  border-bottom: none;
}

kbd {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 4px 10px;
  background-color: var(--bg-card-subtle);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-pill);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

/* footer */
.app-footer {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 14px 24px;
  background-color: var(--bg-card);
  border-top: 1px solid var(--border-subtle);
  flex-wrap: wrap;
  gap: 12px;
}

.footer-nav {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.footer-nav-btn {
  font-family: var(--font-sans);
  font-size: 0.88rem;
  font-weight: 600;
  padding: 7px 18px;
  border-radius: var(--radius-pill);
  border: 1px solid transparent;
  background-color: var(--bg-card-subtle);
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.2s ease;
  user-select: none;
}

.footer-nav-btn:hover {
  background-color: var(--vibrant-primary-light);
  color: var(--vibrant-primary);
  border-color: rgba(99, 102, 241, 0.2);
}

.footer-nav-btn.active {
  background: linear-gradient(135deg, var(--vibrant-primary), var(--vibrant-primary-hover));
  color: #ffffff;
  box-shadow: 0 3px 12px rgba(99, 102, 241, 0.35);
}

.footer-info {
  display: flex;
  align-items: center;
}

.footer-shortcuts {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-muted);
  background-color: var(--bg-card-subtle);
  padding: 5px 14px;
  border-radius: var(--radius-pill);
  border: 1px solid var(--border-subtle);
}

@media (max-width: 640px) {
  body {
    padding: 0;
  }
  #app {
    min-height: 100vh;
    border-radius: 0;
    border: none;
  }
  .app-header {
    flex-direction: column;
    align-items: stretch;
  }
  .header-right {
    justify-content: flex-start;
  }
  .quick-nav {
    overflow-x: auto;
    width: 100%;
    padding-bottom: 2px;
  }
  .kanji-glyph {
    font-size: 5rem;
  }
  .quiz-kanji-glyph {
    font-size: 5.5rem;
  }
  .rating-buttons-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.05ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}