:root {
  --dos-blue: #0000a8;
  --dos-blue-light: #5c5cc0;
  --dos-white: #ffffff;
  --dos-yellow: #ffff55;
  --dos-gray: #aaaaaa;
  --dos-dark: #000000;
  --font-dos: "VT323", "Courier New", monospace;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background: #1a1a2e;
  color: var(--dos-white);
  font-family: var(--font-dos);
  overflow: hidden;
}

.screen {
  position: fixed;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
}

.screen.active {
  display: flex;
}

/* The defrag canvas screen stays clipped to viewport; the start and
   complete screens may need to scroll when zoomed in or on short viewports. */
#start-screen.active,
#complete-screen.active {
  align-items: flex-start;
  overflow-y: auto;
  padding: clamp(12px, 4vh, 48px) 0;
}

/* ---------- Start screen ---------- */

#start-screen {
  background: linear-gradient(135deg, #0a0a23 0%, #1a1a3e 100%);
}

#github-link {
  position: absolute;
  top: 10px;
  right: 12px;
  color: var(--dos-white);
  opacity: 0.6;
  transition: opacity 0.15s ease, transform 0.15s ease;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

#github-link:hover {
  opacity: 1;
  transform: scale(1.08);
}

#github-link svg {
  display: block;
}

.start-card {
  position: relative;
  width: min(480px, 92vw);
  margin: auto;
  background: var(--dos-blue);
  border: 3px double var(--dos-white);
  padding: clamp(16px, 3vh, 28px) clamp(20px, 4vw, 32px);
  box-shadow: 8px 8px 0 rgba(0, 0, 0, 0.5);
}

.start-card h1 {
  font-family: var(--font-dos);
  color: var(--dos-yellow);
  font-size: clamp(24px, 4vw, 36px);
  letter-spacing: 2px;
  margin: 0 0 6px;
  text-align: center;
}

.tagline {
  text-align: center;
  margin: 0 0 clamp(14px, 2.5vh, 24px);
  color: var(--dos-white);
  font-size: clamp(15px, 1.4vw, 18px);
  opacity: 0.85;
}

.field {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: clamp(10px, 1.6vh, 16px);
  font-size: 20px;
}

.field.checkbox {
  flex-direction: row;
  align-items: center;
  gap: 10px;
}

.field span {
  color: var(--dos-yellow);
}

.field select,
.field input[type="number"] {
  font-family: var(--font-dos);
  font-size: 20px;
  background: var(--dos-dark);
  color: var(--dos-white);
  border: 2px solid var(--dos-white);
  padding: 6px 10px;
  outline: none;
}

.field select:focus {
  border-color: var(--dos-yellow);
}

.field input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--dos-yellow);
}

.field input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 12px;
  background: var(--dos-dark);
  border: 2px solid var(--dos-white);
  outline: none;
  cursor: pointer;
  padding: 0;
}

.field input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 18px;
  height: 22px;
  background: var(--dos-yellow);
  border: 2px solid var(--dos-white);
  cursor: pointer;
}

.field input[type="range"]::-moz-range-thumb {
  width: 18px;
  height: 22px;
  background: var(--dos-yellow);
  border: 2px solid var(--dos-white);
  border-radius: 0;
  cursor: pointer;
}

.speed-labels {
  display: flex;
  justify-content: space-between;
  margin-top: 4px;
  font-size: 16px;
  color: var(--dos-white);
  opacity: 0.85;
}

#start-btn,
#rerun-btn,
#back-btn {
  display: block;
  width: 100%;
  margin-top: 12px;
  padding: 12px;
  font-family: var(--font-dos);
  font-size: 24px;
  letter-spacing: 3px;
  color: var(--dos-dark);
  background: var(--dos-yellow);
  border: 3px solid var(--dos-white);
  cursor: pointer;
  transition: transform 0.06s ease;
}

#start-btn:hover,
#rerun-btn:hover,
#back-btn:hover {
  background: var(--dos-white);
}

#start-btn:active,
#rerun-btn:active,
#back-btn:active {
  transform: translate(2px, 2px);
}

.hint {
  text-align: center;
  margin: 18px 0 0;
  font-size: 16px;
  opacity: 0.75;
}

kbd {
  background: var(--dos-dark);
  border: 1px solid var(--dos-white);
  padding: 1px 6px;
  font-family: var(--font-dos);
}

/* ---------- Defrag screen ---------- */

#defrag-screen {
  background: var(--dos-blue);
  cursor: none;
}

#defrag-canvas {
  width: 100vw;
  height: 100vh;
  display: block;
  image-rendering: pixelated;
  image-rendering: crisp-edges;
}

/* ---------- Complete screen ---------- */

/* Rendered as an overlay on top of the defrag canvas — the canvas keeps
   showing the final consolidated state behind the popup. */
#complete-screen {
  background: rgba(0, 0, 0, 0.45);
}

.complete-card {
  width: min(520px, 92vw);
  margin: auto;
  background: var(--dos-blue);
  border: 3px double var(--dos-white);
  padding: clamp(20px, 3vh, 32px);
  text-align: center;
}

.complete-card h2 {
  font-family: var(--font-dos);
  color: var(--dos-yellow);
  font-size: 32px;
  letter-spacing: 2px;
  margin: 0 0 16px;
}

.complete-card p {
  font-size: 20px;
  margin: 8px 0;
}

.complete-actions {
  display: flex;
  gap: 12px;
  margin-top: 20px;
}

.complete-actions button {
  flex: 1;
  margin-top: 0;
}