:root {
  --bg: #f3efe4;
  --ink: #16140f;
  --muted: #5e584c;
  --line: #d9d1c0;
  --panel: #fffdf8;
  --well: #14171d;
  --well-line: #2a3140;
  --target: #ff5a36;
  --target-core: #fff8f2;
  --focus: #0b6e5b;
  --miss: #f3c14a;
  --hit: #7dffb3;
  --plot: #0b6e5b;
  --plot-point: #c2410c;
  --radius: 12px;
}

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

html,
body {
  margin: 0;
  padding: 0;
}

html {
  color-scheme: light;
}

body {
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.45;
  max-width: 960px;
  margin: 0 auto;
  padding: 12px 12px 40px;
  overflow-x: hidden;
}

.site-header {
  display: flex;
  flex-direction: column;
  gap: 2px;
  margin-bottom: 10px;
}

h1,
h2 {
  margin: 0;
  letter-spacing: -0.02em;
}

h1 {
  font-size: 1.15rem;
}

h2 {
  font-size: 0.95rem;
}

.prompt {
  margin: 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.controls {
  display: grid;
  gap: 8px;
  margin-bottom: 10px;
}

.difficulty {
  margin: 0;
  padding: 0;
  border: 0;
  min-width: 0;
}

.difficulty legend {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
  margin-bottom: 4px;
}

.segmented {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px;
}

.segmented label {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--panel);
  font-size: 0.92rem;
  font-weight: 600;
  cursor: pointer;
  touch-action: manipulation;
  user-select: none;
}

.segmented input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.segmented label:has(input:checked) {
  background: var(--ink);
  color: var(--bg);
  border-color: var(--ink);
}

.segmented label:has(input:focus-visible) {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

.control-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px;
}

.control-actions button {
  min-height: 44px;
  min-width: 0;
  padding: 0 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--panel);
  color: var(--ink);
  font: inherit;
  font-size: 0.92rem;
  font-weight: 600;
  cursor: pointer;
  touch-action: manipulation;
}

.control-actions button:focus-visible,
.control-actions button:focus {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

.control-actions button:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.hint {
  margin: 0;
  font-size: 0.8rem;
  color: var(--muted);
}

.experiment {
  position: relative;
  height: clamp(360px, 58vh, 640px);
  background:
    linear-gradient(var(--well-line) 1px, transparent 1px) 0 0 / 32px 32px,
    linear-gradient(90deg, var(--well-line) 1px, transparent 1px) 0 0 / 32px 32px,
    var(--well);
  border-radius: var(--radius);
  overflow: hidden;
  user-select: none;
  -webkit-user-select: none;
  touch-action: none;
}

.experiment.is-miss {
  box-shadow: inset 0 0 0 3px var(--miss);
}

.target {
  position: absolute;
  visibility: hidden;
  width: 56px;
  height: 56px;
  padding: 0;
  border: 2px solid #fff;
  border-radius: 50%;
  background:
    radial-gradient(circle at 50% 50%, var(--target-core) 0 16%, var(--target) 17% 100%);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.35);
  cursor: pointer;
  touch-action: manipulation;
  transform: translate(-50%, -50%);
}

.target.is-ready {
  visibility: visible;
}

.target:focus {
  outline: none;
}

.target:focus-visible {
  outline: 3px solid #8be9c4;
  outline-offset: 4px;
}

.hit-flash {
  position: absolute;
  width: 12px;
  height: 12px;
  border: 3px solid var(--hit);
  border-radius: 50%;
  pointer-events: none;
  opacity: 0;
  transform: translate(-50%, -50%) scale(1);
}

.hit-flash.is-on {
  animation: hit-pulse 150ms ease-out;
}

.experiment.is-hit-static .target {
  filter: brightness(1.25);
}

.stats {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin: 10px 0;
  padding: 10px 12px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.stat {
  min-width: 0;
}

.stat-label {
  display: block;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
}

.stat-value {
  display: block;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 1.05rem;
  font-variant-numeric: tabular-nums;
}

.chart-panel,
.explanation {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 12px;
  margin-bottom: 10px;
}

.chart {
  display: block;
  width: 100%;
  height: auto;
  margin-top: 8px;
}

.equation,
.chart-summary,
.explanation p {
  margin: 8px 0 0;
  font-size: 0.92rem;
}

.equation {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.fit-params {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-top: 8px;
}

.formulas {
  margin: 8px 0 0;
  padding: 10px 12px;
  list-style: none;
  background: var(--bg);
  border-radius: 8px;
}

.formulas li {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.92rem;
}

.formulas li + li {
  margin-top: 6px;
}

.formulas span {
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 0.8rem;
}

.chart-summary,
.explanation p {
  color: var(--ink);
}

.explanation code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.86em;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@keyframes hit-pulse {
  from {
    opacity: 1;
    transform: translate(-50%, -50%) scale(1);
  }
  to {
    opacity: 0;
    transform: translate(-50%, -50%) scale(3.2);
  }
}

@media (min-width: 600px) {
  .segmented {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .stats {
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }
}

@media (min-width: 760px) {
  .controls {
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: end;
  }

  .control-actions {
    min-width: 280px;
  }

  .hint {
    grid-column: 1 / -1;
  }
}

@media (prefers-reduced-motion: reduce) {
  .hit-flash.is-on,
  .experiment.is-miss {
    animation: none;
  }

  .hit-flash.is-on {
    opacity: 1;
  }
}