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

html {
  min-inline-size: 0;
  scroll-padding-block-end: calc(var(--space-4) + env(safe-area-inset-bottom));
  background: var(--paper);
}

body {
  min-inline-size: 0;
  min-block-size: 100vh;
  margin: 0;
  background:
    linear-gradient(rgb(216 79 42 / 4%) 1px, transparent 1px) 0 0 / 100% 32px,
    var(--paper);
  color: var(--ink);
  font-size: 18px;
  line-height: 1.6;
  overflow-wrap: anywhere;
}

button,
input {
  font: inherit;
}

button {
  color: inherit;
}

a {
  color: inherit;
}

#app,
.app-shell {
  min-block-size: 100vh;
}

.app-shell {
  display: grid;
  grid-template-rows: auto 1fr auto;
}

.site-header,
.site-footer,
.main-content {
  inline-size: min(100% - 32px, var(--content-width));
  margin-inline: auto;
}

.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  min-block-size: 76px;
  border-bottom: 1px solid var(--line);
}

.main-content {
  inline-size: min(100% - 32px, var(--screen-width));
  padding-block: clamp(2rem, 5vw, 4.5rem) 6rem;
}

.site-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding-block: var(--space-3);
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: var(--text-small);
}

.site-footer p {
  margin: 0;
}

.screen {
  inline-size: 100%;
}

.start-screen {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: var(--space-5) clamp(2rem, 6vw, 5rem);
  align-items: start;
}

.start-screen__intro {
  position: sticky;
  top: var(--space-4);
}

.start-screen__lead {
  max-inline-size: 31rem;
}

.tutorial-list {
  display: grid;
  gap: var(--space-3);
  margin: 0;
  padding: 0;
  list-style: none;
}

.activity-preview,
.start-button {
  grid-column: 1 / -1;
}

.activity-preview {
  order: 3;
}

.start-button {
  order: 4;
}

.activity-preview ul {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-2);
  margin: 0;
  padding: 0;
  list-style: none;
}

.game-screen {
  display: grid;
  gap: clamp(1.25rem, 4vw, 2rem);
}

.progress-block {
  display: grid;
  gap: var(--space-1);
}

.progress-block__labels {
  display: flex;
  justify-content: space-between;
  gap: var(--space-3);
}

.progress-block__tools {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.problem-heading {
  display: grid;
  gap: 0.15rem;
}

.problem-heading__title-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.equation-board {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  gap: clamp(0.5rem, 2vw, 1rem);
  align-items: stretch;
}

.evidence-card {
  display: flex;
  min-inline-size: 0;
  min-block-size: 154px;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: clamp(0.75rem, 3vw, 1.5rem);
}

.equals-sign {
  align-self: center;
}

.equation-expression {
  display: flex;
  min-inline-size: 0;
  align-items: center;
  justify-content: center;
  gap: clamp(0.2rem, 1vw, 0.5rem);
  white-space: nowrap;
}

.answer-form {
  display: grid;
  gap: var(--space-4);
}

.answer-form fieldset {
  min-inline-size: 0;
  margin: 0;
  padding: 0;
  border: 0;
}

.choice-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: var(--space-2);
}

.choice-grid--judge {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.feedback {
  display: grid;
  gap: var(--space-1);
}

@media (max-width: 720px) {
  .site-header,
  .site-footer,
  .main-content {
    inline-size: min(100% - 24px, var(--content-width));
  }

  .site-header {
    min-block-size: 64px;
  }

  .main-content {
    padding-block-start: 1.25rem;
  }

  .start-screen {
    grid-template-columns: 1fr;
  }

  .start-screen__intro {
    position: static;
  }

  .activity-preview,
  .start-button {
    grid-column: auto;
  }

  .start-button {
    order: 3;
  }

  .activity-preview {
    order: 4;
  }

  .activity-preview ul {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 420px) {
  .start-screen {
    gap: var(--space-3);
  }

  .game-screen {
    gap: var(--space-1);
  }

  .start-screen h1 {
    font-size: clamp(2.25rem, 10vw, 2.6rem);
  }

  .tutorial-list {
    gap: var(--space-2);
  }

  .evidence-card {
    min-block-size: 122px;
    padding-inline: 0.6rem;
  }

  .choice-grid,
  .choice-grid--judge {
    grid-template-columns: 1fr;
  }
}

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