:root {
  --ink: #203029;
  --muted: #65736c;
  --paper: #f8f6f1;
  --surface: #fffdf9;
  --line: rgba(32, 48, 41, 0.13);
  --accent: #397a5d;
  --accent-dark: #285540;
  --wash: #abd8c3;
  --shadow: 0 22px 60px rgba(32, 48, 41, 0.12);
}

* {
  box-sizing: border-box;
}

html {
  min-width: 320px;
  background: var(--paper);
  color: var(--ink);
  font-family: "DM Sans", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  background:
    radial-gradient(circle at 104% 8%, color-mix(in srgb, var(--wash) 42%, transparent) 0 9rem, transparent 9.1rem),
    radial-gradient(circle at -5% 92%, color-mix(in srgb, var(--wash) 28%, transparent) 0 8rem, transparent 8.1rem),
    var(--paper);
}

button,
a {
  font: inherit;
}

.exercise-shell {
  display: flex;
  min-height: 100vh;
  min-height: 100dvh;
  flex-direction: column;
}

.exercise-header {
  display: grid;
  width: min(100% - 28px, 1080px);
  min-height: 68px;
  margin-inline: auto;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  border-bottom: 1px solid var(--line);
}

.back-link {
  display: inline-flex;
  width: fit-content;
  min-height: 44px;
  align-items: center;
  gap: 7px;
  color: var(--ink);
  font-size: 0.86rem;
  font-weight: 700;
  text-decoration: none;
}

.back-link > span:first-child {
  font-size: 1.1rem;
  transition: transform 160ms ease;
}

.back-link:hover > span:first-child {
  transform: translateX(-3px);
}

.exercise-shell :is(a, button):focus-visible {
  outline: 4px solid color-mix(in srgb, var(--accent) 30%, transparent);
  outline-offset: 4px;
}

.activity-label {
  overflow: hidden;
  max-width: calc(100vw - 174px);
  margin: 0;
  font-family: "Nunito", sans-serif;
  font-size: clamp(0.96rem, 4vw, 1.12rem);
  font-weight: 900;
  letter-spacing: -0.025em;
  line-height: 1.1;
  text-overflow: ellipsis;
  text-transform: none;
  white-space: nowrap;
}

.header-spacer {
  display: block;
}

.sound-toggle {
  display: grid;
  width: 42px;
  height: 42px;
  justify-self: end;
  place-items: center;
  border: 1px solid color-mix(in srgb, var(--accent) 22%, var(--line));
  border-radius: 14px;
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-size: 1.1rem;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}

.sound-toggle:hover {
  background: color-mix(in srgb, var(--wash) 28%, white);
}

.sound-toggle:active {
  transform: scale(0.96);
}

[hidden] {
  display: none !important;
}

.start-panel {
  display: none !important;
  width: min(100%, 780px);
}

.start-button {
  display: grid;
  width: 100%;
  min-height: min(43vh, 370px);
  min-height: min(43dvh, 370px);
  grid-template-columns: auto auto;
  align-content: center;
  align-items: center;
  justify-content: center;
  gap: 14px 20px;
  padding: 28px;
  border: 2px solid color-mix(in srgb, var(--accent) 24%, var(--line));
  border-radius: 34px;
  background:
    linear-gradient(145deg, rgba(255, 255, 255, 0.82), rgba(255, 255, 255, 0.32)),
    var(--wash);
  box-shadow: var(--shadow);
  color: var(--accent-dark);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  transition: transform 160ms ease, border-color 160ms ease;
}

.start-button:hover {
  transform: translateY(-3px);
  border-color: var(--accent);
}

.start-button:active {
  transform: scale(0.985);
}

.start-speaker {
  font-size: clamp(3.5rem, 18vw, 6.5rem);
  line-height: 1;
}

.start-play {
  display: grid;
  width: clamp(72px, 21vw, 104px);
  aspect-ratio: 1;
  place-items: center;
  padding-left: 0.08em;
  border-radius: 50%;
  background: var(--accent-dark);
  box-shadow: 0 12px 28px color-mix(in srgb, var(--accent) 30%, transparent);
  color: white;
  font-size: clamp(2.1rem, 9vw, 3.4rem);
}

.start-copy {
  grid-column: 1 / -1;
  color: var(--accent-dark);
  font-size: 0.85rem;
  font-weight: 800;
}

.instruction-replay {
  display: inline-flex;
  min-height: 40px;
  align-items: center;
  gap: 7px;
  margin: 0 0 10px;
  padding: 8px 12px;
  border: 1px solid color-mix(in srgb, var(--accent) 20%, var(--line));
  border-radius: 999px;
  background: var(--surface);
  color: var(--accent-dark);
  cursor: pointer;
  font-size: 0.76rem;
  font-weight: 800;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}

.instruction-replay:hover {
  border-color: var(--accent);
}

.activity {
  display: flex;
  width: min(100% - 28px, 1080px);
  flex: 1;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  margin-inline: auto;
  padding-block: 22px 24px;
  text-align: center;
}

.activity-copy {
  display: none;
}

.eyebrow {
  margin: 0 0 7px;
  color: var(--accent-dark);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.15em;
  text-transform: uppercase;
}

.activity-copy h1 {
  margin: 0;
  font-family: "Nunito", sans-serif;
  font-size: clamp(1.65rem, 7vw, 2.6rem);
  font-weight: 900;
  letter-spacing: -0.045em;
  line-height: 1.05;
}

.activity-copy > p {
  display: none;
}

.keyboard-hint {
  margin: 17px 0 0;
  color: var(--muted);
  font-size: 0.74rem;
}

@media (max-width: 699px) {
  html,
  body {
    position: fixed;
    inset: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    overscroll-behavior: none;
  }

  .exercise-shell {
    height: 100vh;
    height: 100dvh;
    min-height: 0;
    overflow: hidden;
  }

  .exercise-header {
    flex: 0 0 auto;
  }

  .activity {
    flex: 1 1 0;
    max-height: calc(100dvh - 68px);
    min-height: 0;
    overflow: hidden;
    padding-block: 12px max(10px, env(safe-area-inset-bottom));
    justify-content: center;
  }

  .activity > :is(
    .addition-stage,
    .blend-stage,
    .choice-stage,
    .comparison-stage,
    .counting-stage,
    .letter-stage,
    .listening-stage,
    .number-addition-stage,
    .number-order-stage,
    .number-stage,
    .reading-stage,
    .sight-word-stage,
    .sounds-stage,
    .subtraction-stage
  ) {
    display: flex;
    width: min(100%, 760px);
    max-height: 100%;
    min-height: 0;
    overflow: hidden;
    flex: 1;
    flex-direction: column;
    align-items: stretch;
  }

  .activity > :is(
    .addition-stage,
    .blend-stage,
    .choice-stage,
    .comparison-stage,
    .counting-stage,
    .letter-stage,
    .listening-stage,
    .number-addition-stage,
    .number-order-stage,
    .number-stage,
    .reading-stage,
    .sight-word-stage,
    .sounds-stage,
    .subtraction-stage
  ) > :is(
    .addition-card,
    .comparison-groups,
    .equation-card,
    .letter-card,
    .listen-button,
    .number-card,
    .object-card,
    .picture-card,
    .prompt-card,
    .reading-card,
    .sequence-card,
    .subtraction-card,
    .word-card
  ) {
    flex: 1 1 auto;
    max-height: 100%;
    min-height: 0 !important;
    margin-block-start: auto;
  }

  .activity > :is(
    .addition-stage,
    .blend-stage,
    .choice-stage,
    .comparison-stage,
    .counting-stage,
    .listening-stage,
    .number-addition-stage,
    .number-order-stage,
    .number-stage,
    .reading-stage,
    .sight-word-stage,
    .sounds-stage,
    .subtraction-stage
  ) > :is(
    .answer-options,
    .blend-controls,
    .choice-options,
    .number-actions,
    .reading-controls,
    .word-controls
  ) {
    flex: 0 0 auto;
    margin-top: auto;
  }

  .keyboard-hint {
    display: none;
  }
}

@media (min-width: 700px) {
  .exercise-header,
  .activity {
    width: min(100% - 64px, 1080px);
  }

  .exercise-header {
    min-height: 84px;
  }

  .activity-label {
    max-width: min(58vw, 620px);
    font-size: 1.2rem;
  }

  .activity {
    padding-block: 32px 36px;
  }

  .activity-copy {
    margin-bottom: 22px;
  }

  .start-button {
    min-height: min(47vh, 420px);
    min-height: min(47dvh, 420px);
    border-radius: 42px;
  }
}

@media (max-height: 620px) {
  .activity {
    padding-block: 18px;
  }

  .activity-copy {
    margin-bottom: 14px;
  }

  .activity-copy > p:last-child,
  .keyboard-hint {
    display: none;
  }

  .start-button {
    min-height: 240px;
  }
}

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