:root {
  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;

  --color-bg: #f1f5f9;
  --color-surface: #ffffff;
  --color-surface-soft: #f8fafc;
  --color-border: #e5e7eb;
  --color-border-strong: #93c5fd;
  --color-primary: #1d4ed8;
  --color-primary-dark: #1e40af;
  --color-primary-soft: #eff6ff;
  --color-primary-soft-strong: #dbeafe;
  --color-text: #111827;
  --color-text-muted: #6b7280;
  --color-text-subtle: #374151;
  --color-success: #16a34a;
  --color-success-soft: #dcfce7;
  --color-error: #dc2626;
  --color-error-soft: #fee2e2;
  --color-warning: #f59e0b;
  --color-shadow: rgba(0, 0, 0, 0.08);
  --color-shadow-soft: rgba(0, 0, 0, 0.06);

  --radius-sm: 10px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-pill: 999px;

  --shadow-soft: 0 4px 14px var(--color-shadow-soft);
  --shadow-card: 0 10px 30px var(--color-shadow);

  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 28px;
  --space-8: 32px;

  --text-xs: 0.78rem;
  --text-sm: 0.85rem;
  --text-md: 0.92rem;
  --text-base: 1rem;
  --text-lg: 1.25rem;
  --text-xl: 1.6rem;
  --text-2xl: 2.2rem;
  --text-3xl: 2.6rem;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 24px;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
}

/* ---------- Index page ---------- */
.wrap {
  width: 100%;
  max-width: 900px;
  margin: 0 auto;
}

.wrap > h1 {
  font-size: 1.8rem;
  margin: 0 0 6px;
  text-align: center;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
  margin-bottom: 28px;
}

.nav a {
  padding: 7px 14px;
  font-size: 0.88rem;
  font-weight: 700;
  text-decoration: none;
  color: var(--color-primary);
  background: var(--color-primary-soft);
  border: 2px solid #bfdbfe;
  border-radius: var(--radius-pill);
}

.nav a:hover {
  background: var(--color-primary-soft-strong);
}

.global-score {
  margin: 0 auto 28px;
  padding: 16px 20px;
  text-align: center;
  background: var(--color-surface);
  border-radius: 14px;
  box-shadow: var(--shadow-soft);
}

.global-score h2 {
  margin: 0 0 6px;
  font-size: 1.1rem;
}

.global-score p {
  margin: 0;
  color: var(--color-text);
  font-weight: 700;
}

.global-score-percentage {
  color: var(--color-text-muted);
}

.category {
  margin-bottom: 34px;
}

.category h2 {
  font-size: 1.25rem;
  margin: 0 0 14px;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: 10px;
}

.count {
  font-size: .8rem;
  background: var(--color-primary);
  color: #fff;
  border-radius: var(--radius-pill);
  padding: 2px 11px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 14px;
}

a.card {
  display: flex;
  flex-direction: column;
  gap: 6px;
  background: var(--color-surface);
  border-radius: 14px;
  padding: 18px;
  box-shadow: var(--shadow-soft);
  text-decoration: none;
  color: var(--color-text);
  font-weight: 700;
  font-size: 1rem;
  border: 2px solid transparent;
  transition: all .15s ease;
}

a.card:hover {
  border-color: var(--color-primary);
  transform: translateY(-2px);
}

a.card span {
  font-size: 0.8rem;
  color: var(--color-primary);
  font-weight: 600;
}

a.card .exercise-score {
  color: var(--color-text);
}

a.card .exercise-score-percentage {
  color: var(--color-text-muted);
}

a.card .exercise-score-percentage.score-low {
  color: var(--color-error);
}

a.card .exercise-score-percentage.score-medium,
.global-score-percentage.score-medium {
  color: var(--color-warning);
}

a.card .exercise-score-percentage.score-high,
.global-score-percentage.score-high {
  color: var(--color-success);
}

.global-score-percentage.score-low {
  color: var(--color-error);
}

footer {
  text-align: center;
  color: #9ca3af;
  font-size: .78rem;
  margin-top: 12px;
}

/* ---------- Shared typography ---------- */
h1 {
  font-size: 1.25rem;
  margin: 0 0 4px;
  color: var(--color-primary);
}

.subtitle {
  color: var(--color-text-muted);
  margin: 0 0 18px;
  font-size: .92rem;
}

.card {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  padding: 28px;
  width: 100%;
  max-width: 560px;
  text-align: center;
}

.word-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  margin: 18px 0 6px;
}

.word {
  font-size: var(--text-3xl);
  font-weight: 800;
  min-height: 3.4rem;
  letter-spacing: .5px;
  margin: 18px 0 6px;
}

.word-meaning {
  color: var(--color-text-muted);
  font-size: .85rem;
  margin-bottom: 6px;
}

.word-meaning a {
  color: var(--color-primary);
}

.feedback {
  min-height: 1.7rem;
  font-weight: 600;
  margin-bottom: 12px;
  font-size: 1.02rem;
}

.good {
  color: var(--color-success);
}

.bad {
  color: var(--color-error);
}

.task {
  display: inline-block;
  margin: 10px 0 10px;
  padding: 6px 16px;
  font-size: .9rem;
  font-weight: 700;
  border-radius: var(--radius-pill);
  background: var(--color-primary-soft);
  color: var(--color-primary);
}

.question {
  font-size: var(--text-2xl);
  font-weight: 800;
  margin: 6px 0 14px;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}

.question input,
.answer-row input,
.operation input {
  font-family: inherit;
  font-weight: 800;
  text-align: center;
  border: none;
  border-bottom: 4px solid var(--color-primary);
  background: transparent;
  color: var(--color-text);
  outline: none;
}

.question input {
  width: 120px;
  font-size: 2rem;
}

.question input:disabled,
.answer-row input:disabled,
.operation input:disabled {
  opacity: .75;
}

.answer-row {
  display: flex;
  justify-content: center;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}

.answer-row label {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--color-text-subtle);
}

.answer-row input {
  width: 130px;
  font-size: 1.6rem;
}

.operation {
  font-size: 2.8rem;
  font-weight: 800;
  margin: 16px 0 10px;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.operation .blank {
  display: inline-block;
  min-width: 110px;
  border-bottom: 4px solid var(--color-primary);
}

.operation .unit {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--color-text-subtle);
}

.operation input {
  width: 120px;
  font-size: 2.4rem;
  border-bottom-color: var(--color-primary);
}

.operation input:focus {
  border-bottom-color: #2563eb;
}

.operation .box {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 70px;
  height: 70px;
  border: 4px dashed #93c5fd;
  border-radius: 14px;
  color: #93c5fd;
}

.frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  line-height: 1.15;
  font-size: 2rem;
}

.frac .den {
  border-top: 3px solid var(--color-text);
  padding-top: 2px;
}

.problem {
  background: var(--color-surface-soft);
  border-left: 5px solid var(--color-primary);
  border-radius: 12px;
  padding: 18px 20px;
  margin: 16px 0 14px;
  text-align: left;
  font-size: 1.25rem;
  line-height: 1.55;
  font-weight: 600;
}

.progress {
  color: var(--color-text-muted);
  font-size: .85rem;
  font-weight: 600;
  margin-bottom: 10px;
  min-height: 1.2rem;
}

/* ---------- Controls ---------- */
button {
  font-family: inherit;
  cursor: pointer;
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  transition: background-color .18s ease, border-color .18s ease, color .18s ease,
    box-shadow .18s ease, transform .18s ease;
}

button:focus-visible {
  outline: 3px solid var(--color-border-strong);
  outline-offset: 3px;
}

.buttons {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

button.choice {
  flex: 1 1 30%;
  min-width: 140px;
  padding: 14px 10px;
  font-size: 1rem;
  font-weight: 600;
  border-color: var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface-soft);
  color: var(--color-text);
}

button.choice:hover:not(:disabled):not(.correct-picked):not(.wrong-picked):not(.reveal) {
  border-color: var(--color-primary);
  background: var(--color-primary-soft);
  box-shadow: 0 5px 12px rgba(29, 78, 216, 0.12);
  transform: translateY(-2px);
}

button.choice:disabled {
  cursor: default;
  opacity: .6;
}

button.choice.correct-picked {
  border-color: var(--color-success);
  background: var(--color-success-soft);
}

button.choice.wrong-picked {
  border-color: var(--color-error);
  background: var(--color-error-soft);
}

button.choice.reveal {
  border-color: var(--color-success);
  background: var(--color-success-soft);
}

.selection-box {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 8px 12px;
  margin: 10px auto 8px;
  border-radius: var(--radius-pill);
  background: var(--color-primary-soft);
  color: var(--color-primary);
  font-size: .82rem;
  font-weight: 700;
  max-width: 100%;
  flex-wrap: wrap;
}

.selection-box[hidden],
.buttons[hidden] {
  display: none;
}

.choices {
  display: flex;
  gap: 10px;
  justify-content: center;
  margin: 4px 0 18px;
  flex-wrap: wrap;
}

.choices button {
  padding: 12px 18px;
  font-size: 1rem;
  font-weight: 700;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  color: var(--color-text-subtle);
  cursor: pointer;
  transition: all .15s ease;
  min-width: 84px;
}

.choices button:hover:not(:disabled) {
  border-color: var(--color-primary);
  background: var(--color-primary-soft);
  color: var(--color-primary);
  box-shadow: 0 5px 12px rgba(29, 78, 216, 0.12);
  transform: translateY(-2px);
}

.choices button.selected {
  border-color: var(--color-primary);
  background: var(--color-primary-soft);
  color: var(--color-primary);
  box-shadow: 0 5px 12px rgba(29, 78, 216, 0.12);
}

.choices button:disabled {
  opacity: .55;
  cursor: default;
}

.setting-options {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.setting-options button {
  padding: 7px 12px;
  font-size: .85rem;
  font-weight: 600;
  border: 2px solid var(--color-border);
  border-radius: 10px;
  background: var(--color-surface);
  color: var(--color-text-subtle);
}

.setting-options button:hover {
  border-color: var(--color-border-strong);
}

.setting-options button.active {
  border-color: var(--color-primary);
  background: var(--color-primary-soft);
  color: var(--color-primary);
}

#check {
  padding: 13px 36px;
  font-size: 1rem;
  font-weight: 700;
  border: none;
  border-radius: 14px;
  background-color: var(--color-primary);
  color: #fff;
  box-shadow: 0 8px 18px rgba(29, 78, 216, 0.2);
  margin-bottom: 18px;
}

#check:hover:not(:disabled) {
  background-color: var(--color-primary-dark);
  box-shadow: 0 10px 22px rgba(29, 78, 216, 0.28);
  transform: translateY(-2px);
}

#check:active:not(:disabled) {
  box-shadow: 0 4px 10px rgba(29, 78, 216, 0.18);
  transform: translateY(0);
}

#check:disabled,
#reset:disabled {
  opacity: .6;
  cursor: default;
  box-shadow: none;
  transform: none;
}

#clear-selection,
#reset {
  padding: 11px 26px;
  font-size: .95rem;
  font-weight: 700;
  border: none;
  border-radius: 14px;
  box-shadow: 0 6px 14px rgba(75, 85, 99, 0.18);
}

#clear-selection {
  background: #e5e7eb;
  color: #111827;
}

#clear-selection:hover:not(:disabled) {
  background: #d1d5db;
  box-shadow: 0 8px 18px rgba(75, 85, 99, 0.22);
  transform: translateY(-2px);
}

#reset {
  background: #6b7280;
  color: #fff;
}

#reset:hover {
  background: #4b5563;
  box-shadow: 0 8px 18px rgba(75, 85, 99, 0.26);
  transform: translateY(-2px);
}

#clear-selection:active:not(:disabled),
#reset:active:not(:disabled) {
  box-shadow: 0 4px 10px rgba(75, 85, 99, 0.18);
  transform: translateY(0);
}

#settingsToggle {
  margin: 16px 0 10px;
  padding: 10px 22px;
  font-size: .9rem;
  font-weight: 700;
  border: 2px solid var(--color-border);
  border-radius: 14px;
  background: var(--color-surface-soft);
  color: var(--color-text-subtle);
}

#settingsToggle.solar-settings-toggle {
  margin: 0;
  padding: 11px 26px;
  font-size: .95rem;
}

#settingsToggle:hover {
  border-color: var(--color-border-strong);
  background: var(--color-primary-soft);
  color: var(--color-primary);
  box-shadow: 0 5px 12px rgba(29, 78, 216, 0.1);
  transform: translateY(-2px);
}

#settingsToggle:active {
  box-shadow: none;
  transform: translateY(0);
}

#settingsToggle .arrow {
  display: inline-block;
  transition: transform .2s ease;
}

#settingsToggle.open .arrow {
  transform: rotate(180deg);
}

/* ---------- Forms and settings ---------- */
.settings {
  background: var(--color-surface-soft);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  text-align: left;
  display: none;
  margin-top: 4px;
  margin-bottom: 18px;
}

.settings.open {
  display: block;
}

.setting-row {
  margin-bottom: 12px;
}

.setting-row:last-child {
  margin-bottom: 0;
}

.setting-label {
  font-size: .78rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--color-text-muted);
  font-weight: 700;
  margin-bottom: 5px;
}

select {
  width: 100%;
  padding: 9px 12px;
  font-size: .95rem;
  font-weight: 600;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-text-subtle);
  cursor: pointer;
  font-family: inherit;
}

select:focus {
  outline: none;
  border-color: var(--color-border-strong);
}

.hint {
  color: #9ca3af;
  font-size: .78rem;
  margin-top: 12px;
}

/* ---------- Badges and score ---------- */
.tense-badge {
  display: inline-block;
  margin-bottom: 10px;
  padding: 5px 14px;
  font-size: .85rem;
  font-weight: 700;
  border-radius: var(--radius-pill);
  background: var(--color-primary-soft);
  color: var(--color-primary);
}

.score {
  background: var(--color-surface-soft);
  border-radius: var(--radius-md);
  padding: 14px;
  margin-bottom: 14px;
}

.score .label {
  color: var(--color-text-muted);
  font-size: .8rem;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.score .numbers {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--color-primary);
}

.score .pct {
  font-size: 1.05rem;
  color: var(--color-success);
  font-weight: 700;
  margin-top: 2px;
}

/* ---------- Search icon ---------- */
a.search-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--color-primary-soft);
  border: 2px solid #bfdbfe;
  color: var(--color-primary);
  cursor: pointer;
  transition: all .15s ease;
  flex: 0 0 auto;
  text-decoration: none;
}

a.search-icon:hover {
  background: var(--color-primary-soft-strong);
  transform: scale(1.08);
}

a.search-icon svg {
  width: 20px;
  height: 20px;
}