:root {
  --bg: #f4f4f5;
  --card-bg: #ffffff;
  --text: #1c1c1e;
  --muted: #6b7280;
  --border: #d4d4d8;
  --accent: #2563eb;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #18181b;
    --card-bg: #232326;
    --text: #f4f4f5;
    --muted: #9ca3af;
    --border: #3f3f46;
    --accent: #3b82f6;
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 2rem 1rem;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

.card {
  width: 100%;
  max-width: 32rem;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
}

h1 {
  margin: 0 0 0.4rem;
  font-size: 1.25rem;
}

.note {
  margin: 0 0 1.25rem;
  color: var(--muted);
  font-size: 0.85rem;
}

.field {
  margin-bottom: 1.25rem;
}

.field label {
  display: block;
  font-size: 0.9rem;
  margin-bottom: 0.4rem;
}

select,
input[type="number"],
input[type="text"] {
  width: 100%;
  padding: 0.5rem;
  border: 1px solid var(--border);
  border-radius: 0.4rem;
  background: var(--card-bg);
  color: var(--text);
  font: inherit;
}

.convert-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

/* display: flex by class by default beats the browser's [hidden] default —
   an explicit override is needed to actually hide these when toggled by JS. */
.convert-row[hidden],
.color-row[hidden] {
  display: none;
}

.convert-col {
  flex: 1 1 10rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

#result {
  display: block;
  padding: 0.5rem;
  border: 1px solid var(--border);
  border-radius: 0.4rem;
  background: var(--bg);
  color: var(--text);
  font-variant-numeric: tabular-nums;
  min-height: 1.2rem;
  overflow-wrap: anywhere;
}

button#swap {
  flex: 0 0 auto;
  width: 2.5rem;
  height: 2.5rem;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: var(--card-bg);
  color: var(--accent);
  font-size: 1.1rem;
  cursor: pointer;
}

button#swap:hover {
  filter: brightness(1.05);
}

.color-row {
  display: flex;
  gap: 1rem;
  align-items: flex-start;
}

.color-swatches {
  flex: 0 0 auto;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.color-swatches input[type="color"] {
  width: 3.5rem;
  height: 3.5rem;
  padding: 0.15rem;
  border: 1px solid var(--border);
  border-radius: 0.4rem;
  cursor: pointer;
}

/* Šachovnice za náhledem, aby byla průhlednost vidět — nativní <input type="color">
   alfu nezobrazuje ani nepodporuje, proto je náhled samostatný prvek. */
.color-preview {
  position: relative;
  width: 3.5rem;
  height: 3.5rem;
  border-radius: 0.4rem;
  border: 1px solid var(--border);
  background-image: repeating-conic-gradient(#ccc 0% 25%, #fff 0% 50%);
  background-size: 12px 12px;
  overflow: hidden;
}

.color-preview::after {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--preview-color, transparent);
}

.alpha-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.4rem;
}

.alpha-row output {
  font-variant-numeric: tabular-nums;
  color: var(--muted);
  font-size: 0.9rem;
}

#alpha-value {
  width: 100%;
}

.color-fields {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.color-fields .field {
  margin-bottom: 0;
}

.color-fields input[type="text"] {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}