:root {
  --bg: #f6f7f9;
  --panel: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --line: #e5e7eb;
  --accent: #c2410c;
  --warn-bg: #fff7ed;
  --warn-line: #fdba74;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #111418;
    --panel: #181c21;
    --text: #e5e7eb;
    --muted: #9ca3af;
    --line: #2b3138;
    --accent: #fb923c;
    --warn-bg: #2a1d12;
    --warn-line: #9a4b16;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

header, .layout, .about { max-width: 1000px; margin: 0 auto; padding: 0 16px; }
header { padding-top: 20px; }
h1 { margin: 0 0 10px; font-size: 24px; }
h2 { margin: 0 0 10px; font-size: 16px; }

.warning {
  background: var(--warn-bg);
  border: 1px solid var(--warn-line);
  border-radius: 6px;
  padding: 10px 12px;
  margin: 0 0 16px;
}

.layout {
  display: grid;
  grid-template-columns: 300px minmax(0, 1fr);
  gap: 16px;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px;
}

form label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
  font-size: 14px;
}

input, select {
  width: 150px;
  font: inherit;
  padding: 4px 6px;
  border: 1px solid var(--line);
  border-radius: 5px;
  background: var(--bg);
  color: var(--text);
}

input:focus-visible, select:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
input:invalid { border-color: #dc2626; }
.hint, .legend { color: var(--muted); font-size: 13px; }

.big { font-size: 18px; margin: 0 0 8px; }
#rfs { font-size: 32px; font-weight: 700; color: var(--accent); }
#curve { display: block; width: 100%; height: 300px; }

.key { display: inline-block; width: 18px; height: 0; vertical-align: middle; margin: 0 4px 0 10px; }
.key.you { border-top: 3px solid var(--accent); }
.key.avg { border-top: 2px dashed var(--muted); }

.about { padding-top: 8px; padding-bottom: 28px; }
.about a { color: var(--accent); }

@media (max-width: 760px) {
  .layout { grid-template-columns: 1fr; }
  #curve { height: 240px; }
}