html,
body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
  background: #000;
}

body {
  color: white;
  font-family: "Malgun Gothic", sans-serif;
}

#viewport {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100dvh;
  overflow: hidden;
  background: #000;
}

#game-root,
#game-shell {
  position: absolute;
  left: 0;
  top: 0;
  width: 1920px;
  height: 1080px;
  transform-origin: top left;
  overflow: hidden;
  background: #000;
}

#scene-root {
  position: relative;
  width: 1920px;
  height: 1080px;
  overflow: hidden;
  background: #111;
}

#ui-layer,
#overlay-layer {
  position: absolute;
  left: 0;
  top: 0;
  width: 1920px;
  height: 1080px;
  pointer-events: none;
}

#ui-layer > *,
#overlay-layer > * {
  pointer-events: auto;
}

.game-frame {
  position: absolute;
  left: 0;
  top: 0;
  width: 1920px;
  height: 1080px;
  overflow: hidden;
  background: #000;
}

.hidden {
  display: none !important;
}

#boot-screen {
  position: fixed;
  inset: 0;
  background: #000;
  color: white;
  display: flex;
  align-items: flex-end;
  justify-content: flex-start;
  padding: 24px;
  z-index: 9999;
}

.boot-inner h1 {
  margin: 0 0 12px;
  font-size: 56px;
}

.boot-inner p {
  margin: 0;
  font-size: 28px;
}

/* ═══════════════════════════════════════════════════════════
   Edu worksheet design tokens (s11 fraction-card baseline)
   Reuse: var(--edu-worksheet-*) in Stage 1–2 learning panels
   ═══════════════════════════════════════════════════════════ */
:root {
  --edu-worksheet-width: 1080px;
  --edu-worksheet-height: 580px;
  --edu-worksheet-padding: 36px 42px 32px;

  --edu-worksheet-font: "Pretendard", "Noto Sans KR", "Segoe UI", sans-serif;
  --edu-worksheet-text-color: #10243f;

  --edu-worksheet-background:
    radial-gradient(circle at top left, rgba(220, 245, 255, 0.65), transparent 35%),
    linear-gradient(180deg, rgba(250, 253, 255, 0.98), rgba(238, 248, 255, 0.96));
  --edu-worksheet-border-width: 1.5px;
  --edu-worksheet-border-color: rgba(120, 200, 255, 0.85);
  --edu-worksheet-radius: 20px;
  --edu-worksheet-shadow:
    0 0 0 1px rgba(255, 255, 255, 0.7),
    0 0 28px rgba(90, 190, 255, 0.28),
    0 18px 45px rgba(0, 0, 0, 0.35);
  --edu-worksheet-backdrop: blur(10px);

  --edu-worksheet-title-size: 30px;
  --edu-worksheet-title-weight: 800;
  --edu-worksheet-title-color: #17384d;
  --edu-worksheet-title-letter-spacing: 0.02em;
  --edu-worksheet-header-border: 1px solid rgba(180, 220, 240, 0.65);
}

.edu-worksheet-title,
.stage1-same-amount-tutorial .stage1-sa-compact-title,
.stage1-same-amount-tutorial .stage1-sa-tutorial .stage1-sa-compact-title.edu-worksheet-title,
.stage1-white-worksheet .s12-activity-title,
.stage1-white-worksheet .s12-activity-title--summary,
.stage1-white-worksheet .s12-learning-title,
.s21-sheet-title,
.corridor-puzzle-card.edu-worksheet-panel .edu-worksheet-title,
.corridor-puzzle-card.edu-worksheet-panel h2.edu-worksheet-title {
  margin: 0;
  color: var(--edu-worksheet-title-color);
  font-family: var(--edu-worksheet-font);
  font-size: var(--edu-worksheet-title-size);
  font-weight: var(--edu-worksheet-title-weight);
  line-height: 1.2;
  letter-spacing: var(--edu-worksheet-title-letter-spacing);
  text-align: left;
  text-shadow: none;
}

.edu-worksheet-panel,
.stage1-same-amount-tutorial .stage1-sa-recovery-card.fraction-card,
.stage1-summary-panel.stage1-white-worksheet.fraction-card,
.stage1-white-worksheet.s12-learning-panel,
.stage1-white-worksheet.s12-multiply-panel,
.corridor-puzzle-card.s21-learning-card.edu-worksheet-panel,
.corridor-puzzle-card.edu-worksheet-panel {
  box-sizing: border-box;
  color: var(--edu-worksheet-text-color);
  font-family: var(--edu-worksheet-font);
  border: var(--edu-worksheet-border-width) solid var(--edu-worksheet-border-color);
  border-radius: var(--edu-worksheet-radius);
  background: var(--edu-worksheet-background);
  box-shadow: var(--edu-worksheet-shadow);
  backdrop-filter: var(--edu-worksheet-backdrop);
  -webkit-backdrop-filter: var(--edu-worksheet-backdrop);
}

.edu-worksheet-panel--large,
.stage1-summary-panel.stage1-white-worksheet.fraction-card,
.stage1-white-worksheet.s12-learning-panel,
.stage1-white-worksheet.s12-multiply-panel,
.corridor-puzzle-card.s21-learning-card.edu-worksheet-panel--large,
body.s21-fixed-viewport-active .corridor-puzzle-card.s21-learning-card {
  width: var(--edu-worksheet-width);
  max-width: var(--edu-worksheet-width);
  height: var(--edu-worksheet-height);
  min-height: var(--edu-worksheet-height);
  max-height: var(--edu-worksheet-height);
  padding: var(--edu-worksheet-padding);
}

.edu-worksheet-header,
.stage1-white-worksheet .s12-activity-header,
.s21-sheet-header {
  margin: 0 0 18px;
  padding: 0 0 14px;
  text-align: left;
  border-bottom: var(--edu-worksheet-header-border);
}

/* ═══════════════════════════════════════════════════════════
   Edu blank input (fraction / equation blanks on white worksheets)
   Classes: .edu-blank-input, .is-correct / .is-ok, .is-error / .is-warn
   ═══════════════════════════════════════════════════════════ */
:root {
  --edu-blank-input-border: 2px solid rgba(90, 180, 240, 0.95);
  --edu-blank-input-border-focus: #35c9ff;
  --edu-blank-input-bg: rgba(255, 255, 255, 0.96);
  --edu-blank-input-color: #0d2744;
  --edu-blank-input-shadow:
    0 0 10px rgba(80, 190, 255, 0.22),
    inset 0 0 0 1px rgba(255, 255, 255, 0.8);
  --edu-blank-input-shadow-focus:
    0 0 0 3px rgba(53, 201, 255, 0.22),
    0 0 14px rgba(53, 201, 255, 0.35);
  --edu-blank-input-correct-border: #45d8ff;
  --edu-blank-input-correct-shadow:
    0 0 0 3px rgba(69, 216, 255, 0.2),
    0 0 18px rgba(69, 216, 255, 0.5);
  --edu-blank-input-error-border: rgba(245, 158, 11, 0.72);
  --edu-blank-input-error-bg: rgba(255, 251, 235, 0.98);
  --edu-blank-input-error-shadow:
    0 0 0 3px rgba(251, 191, 36, 0.14),
    0 0 12px rgba(245, 158, 11, 0.18);
  --edu-blank-input-font-size: 30px;
}

.edu-blank-input {
  box-sizing: border-box;
  padding: 0;
  border: var(--edu-blank-input-border);
  border-radius: 10px;
  background: var(--edu-blank-input-bg);
  color: var(--edu-blank-input-color);
  font-weight: 900;
  font-size: var(--edu-blank-input-font-size, 30px);
  line-height: 1;
  text-align: center;
  outline: none;
  box-shadow: var(--edu-blank-input-shadow);
  opacity: 1;
  -webkit-text-fill-color: var(--edu-blank-input-color);
  caret-color: var(--edu-blank-input-color);
}

.edu-blank-input--md {
  width: 57px;
  height: 57px;
  min-width: 57px;
  min-height: 57px;
}

.edu-blank-input--sm {
  width: 40px;
  height: 40px;
  min-width: 40px;
  min-height: 40px;
  border-radius: 6px;
}

.edu-blank-input:focus,
.edu-blank-input:focus-visible {
  border-color: var(--edu-blank-input-border-focus);
  box-shadow: var(--edu-blank-input-shadow-focus);
}

.edu-blank-input.is-correct,
.edu-blank-input.is-ok,
.edu-blank-input.correct {
  border-color: var(--edu-blank-input-correct-border);
  background: rgba(230, 250, 255, 0.98);
  box-shadow: var(--edu-blank-input-correct-shadow);
}

.edu-blank-input.is-error,
.edu-blank-input.is-warn {
  border-color: var(--edu-blank-input-error-border);
  background: var(--edu-blank-input-error-bg);
  color: var(--edu-blank-input-color);
  -webkit-text-fill-color: var(--edu-blank-input-color);
  box-shadow: var(--edu-blank-input-error-shadow);
}

.edu-blank-input.is-error:focus,
.edu-blank-input.is-error:focus-visible,
.edu-blank-input.is-warn:focus,
.edu-blank-input.is-warn:focus-visible {
  border-color: rgba(245, 158, 11, 0.82);
  box-shadow:
    0 0 0 3px rgba(251, 191, 36, 0.18),
    0 0 12px rgba(245, 158, 11, 0.22);
}

.edu-blank-input:disabled:not([readonly]) {
  opacity: 0.45;
  border-color: rgba(120, 190, 240, 0.35);
  background: rgba(240, 248, 255, 0.72);
  color: rgba(13, 39, 68, 0.38);
  -webkit-text-fill-color: rgba(13, 39, 68, 0.38);
  cursor: not-allowed;
  box-shadow: none;
}

.edu-blank-input[readonly] {
  color: var(--edu-blank-input-color);
  opacity: 1;
  -webkit-text-fill-color: var(--edu-blank-input-color);
}

.edu-fraction-blank-line {
  display: block;
  border-radius: 999px;
  background: #0d2744;
}

.edu-fraction-blank-line--md {
  width: 57px;
  height: 3px;
  margin: 5px 0;
}

.edu-fraction-blank-line--sm {
  width: 40px;
  height: 2px;
  margin: 0;
}