:root {
  color-scheme: light;
  --ink: #1f2328;
  --muted: #68717a;
  --paper: #fffaf2;
  --surface: #ffffff;
  --line: #d8dde4;
  --red: #b51d2a;
  --red-soft: #f8dde0;
  --blue: #2453a6;
  --blue-soft: #e4ecfb;
  --gold: #d9971d;
  --green: #1d7355;
  --charcoal: #30343a;
  --shadow: 0 18px 48px rgba(31, 35, 40, 0.13);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Arial, sans-serif;
  line-height: 1.5;
}

button,
input,
select {
  font: inherit;
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

button:disabled {
  cursor: progress;
  opacity: 0.65;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  min-height: 72px;
  padding: 12px clamp(18px, 4vw, 56px);
  background: rgba(255, 250, 242, 0.94);
  border-bottom: 1px solid rgba(216, 221, 228, 0.85);
  backdrop-filter: blur(18px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: inherit;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: 8px;
  background: var(--red);
  color: white;
  font-size: 1.8rem;
  font-weight: 900;
}

.brand strong,
.brand small {
  display: block;
}

.brand strong {
  font-size: 0.98rem;
}

.brand small {
  color: var(--muted);
  font-size: 0.78rem;
}

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

.nav a {
  border-radius: 8px;
  color: var(--charcoal);
  padding: 8px 11px;
  text-decoration: none;
}

.nav a:hover,
.nav a:focus-visible {
  background: var(--blue-soft);
  color: var(--blue);
  outline: none;
}

main {
  overflow: hidden;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 0.92fr) minmax(320px, 1.08fr);
  gap: clamp(26px, 5vw, 70px);
  align-items: center;
  padding: clamp(34px, 6vw, 72px) clamp(18px, 4vw, 56px) clamp(28px, 5vw, 60px);
}

.hero-copy {
  max-width: 760px;
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--red);
  font-size: 0.78rem;
  font-weight: 850;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  overflow-wrap: anywhere;
}

h1 {
  margin: 0;
  color: var(--charcoal);
  font-size: clamp(3.25rem, 7.4vw, 7rem);
  line-height: 0.92;
  letter-spacing: 0;
  overflow-wrap: normal;
  word-break: normal;
}

h2 {
  margin: 0;
  font-size: clamp(1.75rem, 4vw, 3rem);
  line-height: 1.08;
  letter-spacing: 0;
}

.hero-subtitle {
  max-width: 600px;
  margin: 22px 0 0;
  color: var(--muted);
  font-size: clamp(1rem, 1.8vw, 1.2rem);
}

.hero-actions,
.quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 28px;
}

.primary-action,
.secondary-action,
.button-reset {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  border-radius: 8px;
  cursor: pointer;
  text-decoration: none;
}

.primary-action {
  gap: 10px;
  border: 0;
  background: var(--red);
  color: #fff;
  padding: 0 18px;
  box-shadow: 0 12px 26px rgba(181, 29, 42, 0.22);
}

.primary-action:hover,
.primary-action:focus-visible {
  background: #941724;
  outline: none;
}

.secondary-action,
.button-reset {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--charcoal);
  padding: 0 16px;
}

.secondary-action:hover,
.secondary-action:focus-visible,
.button-reset:hover,
.button-reset:focus-visible {
  border-color: var(--blue);
  color: var(--blue);
  outline: none;
}

.compact {
  min-height: 40px;
  padding: 0 14px;
}

.hero-media {
  margin: 0;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.hero-media img {
  display: block;
  width: 100%;
  aspect-ratio: 4 / 3;
  object-fit: cover;
  object-position: top center;
}

.control-strip {
  display: grid;
  grid-template-columns: minmax(130px, 0.72fr) minmax(210px, 1.35fr) minmax(120px, 0.75fr) minmax(120px, 0.75fr) auto auto;
  gap: 12px;
  align-items: end;
  margin: 0 clamp(18px, 4vw, 56px);
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.offline-action {
  white-space: nowrap;
}

.control-label {
  display: block;
  margin-bottom: 6px;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 850;
  text-transform: uppercase;
}

select,
input[type="search"] {
  width: 100%;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  padding: 0 12px;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--red);
}

.icon-button {
  display: inline-grid;
  place-items: center;
  flex: 0 0 auto;
  width: 42px;
  height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--charcoal);
  cursor: pointer;
}

.icon-button:hover,
.icon-button:focus-visible {
  border-color: var(--red);
  color: var(--red);
  outline: none;
}

.icon-button.large {
  width: 58px;
  height: 58px;
  border-color: transparent;
  background: var(--blue);
  color: #fff;
  font-size: 1.15rem;
}

.section {
  padding: clamp(54px, 8vw, 92px) clamp(18px, 4vw, 56px);
}

.section-band {
  background: #f3f6fb;
  border-block: 1px solid var(--line);
}

.section-heading {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 18px;
  margin-bottom: 24px;
}

.search-wrap {
  width: min(100%, 430px);
}

.alphabet-grid,
.vocab-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(255px, 1fr));
  gap: 14px;
}

.alphabet-card,
.vocab-card,
.dialogue-line,
.sentence-card,
.quiz-panel,
.source-panel,
.word-group-panel {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--surface);
}

.alphabet-card,
.vocab-card {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 12px;
  min-height: 210px;
  padding: 18px;
}

.letter-pair {
  display: flex;
  align-items: baseline;
  gap: 10px;
  line-height: 1;
}

.letter-pair strong {
  color: var(--red);
  font-size: clamp(3rem, 6vw, 4.4rem);
}

.letter-pair span {
  color: var(--red);
  font-size: clamp(2.2rem, 4.5vw, 3.3rem);
  font-weight: 850;
}

.sound {
  margin-top: 10px;
  color: var(--blue);
  font-size: 1.05rem;
  font-weight: 850;
}

.example {
  margin-top: 16px;
  color: var(--charcoal);
  font-size: clamp(1.45rem, 2.8vw, 2.1rem);
  font-weight: 850;
  line-height: 1.15;
}

.meaning,
.note,
.line-meta,
.sentence-meta {
  color: var(--muted);
}

.note {
  margin-top: 10px;
  font-size: 0.9rem;
}

.card-actions {
  display: grid;
  align-content: start;
  gap: 8px;
}

.filter-row,
.tabs,
.letter-row,
.word-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.filter-row {
  justify-content: flex-end;
}

.filter-row button,
.tabs button {
  min-height: 38px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--charcoal);
  cursor: pointer;
  padding: 0 12px;
}

.filter-row button.is-active,
.tabs button.is-active {
  border-color: var(--blue);
  background: var(--blue-soft);
  color: var(--blue);
  font-weight: 850;
}

.word-group-panel {
  padding: 20px;
}

.letter-row {
  margin-bottom: 20px;
}

.letter-chip,
.word-chip,
.category-chip {
  display: inline-flex;
  align-items: center;
  min-height: 34px;
  border-radius: 8px;
  font-weight: 800;
}

.letter-chip {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--blue);
  padding: 0 12px;
}

.word-chip {
  gap: 8px;
  border: 1px solid #d9e0ea;
  background: #fff;
  color: var(--charcoal);
  cursor: pointer;
  padding: 0 9px 0 12px;
}

.word-chip:hover,
.word-chip:focus-visible {
  border-color: var(--red);
  color: var(--red);
  outline: none;
}

.category-chip {
  width: fit-content;
  background: var(--red-soft);
  color: var(--red);
  padding: 0 10px;
  font-size: 0.78rem;
}

.word-dialogues {
  display: grid;
  gap: 12px;
  margin-top: 22px;
}

.mini-dialogue {
  border-top: 1px solid var(--line);
  padding-top: 16px;
}

.mini-dialogue h3 {
  margin: 0 0 10px;
  font-size: 1.05rem;
}

.mini-dialogue-line {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr) auto;
  gap: 10px;
  align-items: center;
  min-height: 48px;
}

.vocab-card {
  min-height: 190px;
}

.vocab-russian,
.line-russian,
.sentence-russian {
  color: var(--charcoal);
  font-weight: 850;
  line-height: 1.16;
}

.vocab-russian {
  font-size: clamp(1.55rem, 3.1vw, 2.4rem);
}

.vocab-meta {
  display: grid;
  gap: 6px;
  margin-top: 14px;
}

.conversation-layout {
  display: grid;
  grid-template-columns: 230px 1fr;
  gap: 18px;
}

.tabs.stacked {
  display: grid;
  align-content: start;
}

.dialogue {
  display: grid;
  gap: 10px;
}

.dialogue-line {
  display: grid;
  grid-template-columns: minmax(52px, 0.12fr) minmax(0, 1fr) auto;
  gap: 14px;
  align-items: center;
  min-height: 86px;
  padding: 14px;
}

.speaker {
  color: var(--red);
  font-size: 1.1rem;
  font-weight: 900;
}

.line-russian {
  font-size: clamp(1.35rem, 2.6vw, 2.2rem);
}

.line-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 6px;
  font-size: 0.92rem;
}

.sentence-blocks {
  display: grid;
  gap: 18px;
}

.sentence-block h3 {
  margin: 0 0 12px;
  color: var(--charcoal);
  font-size: 1.18rem;
}

.sentence-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(290px, 1fr));
  gap: 10px;
}

.sentence-card {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 12px;
  min-height: 132px;
  padding: 16px;
}

.sentence-russian {
  font-size: clamp(1.25rem, 2.4vw, 1.85rem);
}

.sentence-meta {
  display: grid;
  gap: 4px;
  margin-top: 8px;
}

.practice-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(260px, 0.62fr);
  gap: 18px;
}

.quiz-panel {
  padding: 22px;
}

.quiz-prompt {
  min-height: 74px;
  color: var(--charcoal);
  font-size: clamp(1.75rem, 4vw, 3rem);
  font-weight: 900;
  line-height: 1.1;
}

.answers {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  margin-top: 20px;
}

.answer-button {
  min-height: 56px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--charcoal);
  cursor: pointer;
  padding: 10px 12px;
  text-align: left;
}

.answer-button:hover,
.answer-button:focus-visible {
  border-color: var(--blue);
  outline: none;
}

.answer-button.is-correct {
  border-color: var(--green);
  background: #e0f2ea;
}

.answer-button.is-wrong {
  border-color: var(--red);
  background: var(--red-soft);
}

.feedback {
  min-height: 28px;
  margin-top: 14px;
  color: var(--charcoal);
  font-weight: 850;
}

.source-panel {
  overflow: hidden;
}

.source-panel img {
  display: block;
  width: 100%;
  height: 100%;
  min-height: 320px;
  object-fit: cover;
  object-position: top center;
}

.empty-state {
  grid-column: 1 / -1;
  border: 1px dashed var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--muted);
  padding: 28px;
  text-align: center;
}

.footer {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  padding: 22px clamp(18px, 4vw, 56px) 34px;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 960px) {
  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .nav {
    width: 100%;
    overflow-x: auto;
    padding-bottom: 2px;
  }

  .hero,
  .conversation-layout,
  .practice-layout {
    grid-template-columns: 1fr;
  }

  .control-strip {
    grid-template-columns: 1fr 1fr;
  }

  .tabs.stacked {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  .topbar {
    gap: 10px;
    min-height: 112px;
    padding-top: 10px;
    padding-bottom: 10px;
  }

  .hero {
    gap: 18px;
    padding-top: 26px;
    padding-bottom: 20px;
  }

  .hero-media img {
    aspect-ratio: 16 / 9;
    max-height: 260px;
  }

  .hero-actions {
    margin-top: 22px;
  }

  .section-heading,
  .footer {
    align-items: stretch;
    flex-direction: column;
  }

  .filter-row {
    justify-content: flex-start;
  }

  .control-strip,
  .answers {
    grid-template-columns: 1fr;
  }

  .alphabet-card,
  .vocab-card,
  .dialogue-line,
  .sentence-card,
  .mini-dialogue-line {
    grid-template-columns: 1fr;
  }

  .dialogue-line .icon-button,
  .vocab-card .icon-button,
  .sentence-card .icon-button,
  .mini-dialogue-line .icon-button {
    justify-self: start;
  }

  .tabs.stacked {
    grid-template-columns: 1fr;
  }

  h1 {
    font-size: clamp(3rem, 14vw, 4.3rem);
    overflow-wrap: normal;
    word-break: normal;
  }
}