:root {
  color-scheme: light dark;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen,
    Ubuntu, Cantarell, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    "Liberation Mono", monospace;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;

  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;

  --transition: 150ms ease;

  --bg: light-dark(#fafaf7, #0e1116);
  --surface: light-dark(#ffffff, #171b22);
  --surface-muted: light-dark(#f4f4f0, #1f242d);
  --text: light-dark(#161616, #ececec);
  --text-muted: light-dark(#5f6168, #9ca0a8);
  --border: light-dark(#e4e4df, #2a3038);
  --accent: light-dark(#2563eb, #6aa3ff);
  --accent-contrast: light-dark(#ffffff, #0e1116);
  --accent-soft: light-dark(rgb(37 99 235 / 0.1), rgb(106 163 255 / 0.14));
  --danger: light-dark(#b91c1c, #f87171);
  --success: light-dark(#16a34a, #4ade80);
  --success-contrast: light-dark(#ffffff, #0e1116);
  --focus-ring: light-dark(rgb(37 99 235 / 0.45), rgb(106 163 255 / 0.55));
  --shadow-sm: light-dark(
    0 1px 2px rgb(0 0 0 / 0.04),
    0 1px 2px rgb(0 0 0 / 0.35)
  );
  --shadow-md: light-dark(
    0 4px 16px rgb(0 0 0 / 0.06),
    0 4px 16px rgb(0 0 0 / 0.45)
  );
  --caret: light-dark(
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 12 8' fill='none' stroke='%235f6168' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M1 1.5l5 5 5-5'/%3E%3C/svg%3E"),
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 12 8' fill='none' stroke='%239ca0a8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M1 1.5l5 5 5-5'/%3E%3C/svg%3E")
  );
}

:root[data-theme="light"] {
  color-scheme: light;
}
:root[data-theme="dark"] {
  color-scheme: dark;
}

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

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

body {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.5;
  /* Disables iOS Safari double-tap-to-zoom. Pinch-zoom still works. */
  touch-action: manipulation;
  transition:
    background-color var(--transition),
    color var(--transition);
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

.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;
}

.skip-link {
  position: absolute;
  top: -40px;
  left: var(--space-4);
  background: var(--accent);
  color: var(--accent-contrast);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  text-decoration: none;
  z-index: 10;
}
.skip-link:focus {
  top: var(--space-4);
}

/* Header */
.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) var(--space-5);
  max-width: 720px;
  width: 100%;
  margin: 0 auto;
}

.site-title {
  margin: 0;
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.header-actions {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text);
  cursor: pointer;
  text-decoration: none;
  transition:
    background-color var(--transition),
    border-color var(--transition);
}
@media (hover: hover) {
  .icon-btn:hover {
    background: var(--surface-muted);
  }
}
.icon-btn .icon {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}
.icon--sun,
.icon--moon {
  display: none;
}
/* Default (no explicit theme): match system. Moon = "click to go dark". */
:root:not([data-theme]) .icon--moon {
  display: block;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) .icon--moon {
    display: none;
  }
  :root:not([data-theme]) .icon--sun {
    display: block;
  }
}
:root[data-theme="light"] .icon--moon {
  display: block;
}
:root[data-theme="dark"] .icon--sun {
  display: block;
}

/* Layout */
.container {
  flex: 1;
  width: 100%;
  max-width: 720px;
  margin: 0 auto;
  padding: var(--space-4) var(--space-5) var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

/* Result panel */
.result-panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-6) var(--space-4);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}

.result {
  font-family: var(--font-mono);
  font-size: clamp(1.4rem, 4.5vw, 2rem);
  font-weight: 500;
  line-height: 1.2;
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  background: var(--surface-muted);
  cursor: pointer;
  user-select: all;
  max-width: 100%;
  word-break: break-all;
  text-align: center;
  /* Reserve two lines so wrapping doesn't push the options below. */
  min-height: calc(1.2em * 2 + var(--space-3) * 2);
  display: flex;
  align-items: center;
  justify-content: center;
  transition:
    background-color var(--transition),
    transform var(--transition);
}
@media (hover: hover) {
  .result:hover {
    background: var(--accent-soft);
  }
}
.result:active {
  transform: scale(0.99);
}
.result[data-state="error"] {
  color: var(--danger);
}

.actions {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
  justify-content: center;
}

.btn {
  font: inherit;
  font-weight: 500;
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  transition:
    background-color var(--transition),
    border-color var(--transition),
    transform var(--transition);
}
.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}
.btn:not(:disabled):active {
  transform: translateY(1px);
}

.btn--primary {
  background: var(--accent);
  color: var(--accent-contrast);
  border-color: var(--accent);
}
@media (hover: hover) {
  .btn--primary:not(:disabled):hover {
    filter: brightness(1.05);
  }
}

.btn--secondary {
  background: var(--surface);
  color: var(--text);
  border-color: var(--border);
}
@media (hover: hover) {
  .btn--secondary:not(:disabled):hover {
    background: var(--surface-muted);
  }
}
.btn--secondary.is-copied {
  background: var(--success);
  color: var(--success-contrast);
  border-color: var(--success);
}
@media (hover: hover) {
  .btn--secondary.is-copied:not(:disabled):hover {
    background: var(--success);
    color: var(--success-contrast);
    border-color: var(--success);
  }
}

/* Reserve width so a text swap (e.g. Copy → Copied!) doesn't reflow. */
.btn--fixed-width {
  min-width: 7rem;
}

.toast {
  margin: 0;
  padding: var(--space-2) var(--space-3);
  background: var(--accent-soft);
  color: var(--accent);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 500;
}

/* Options card */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  box-shadow: var(--shadow-sm);
}

.card-title {
  margin: 0 0 var(--space-4);
  font-size: 0.95rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.options-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--space-4);
}

.field {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.field-label {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
}

.field-hint {
  font-size: 0.78rem;
  color: var(--text-muted);
  min-height: 1.1em;
}

.field select,
.field input[type="number"] {
  font: inherit;
  font-size: 1rem;
  line-height: 1.5;
  color: var(--text);
  background: var(--surface-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: var(--space-3);
  width: 100%;
  min-height: 2.75rem;
  transition:
    border-color var(--transition),
    background-color var(--transition);
}
.field select {
  appearance: none;
  -webkit-appearance: none;
  background-image: var(--caret);
  background-repeat: no-repeat;
  background-position: right var(--space-3) center;
  background-size: 12px 8px;
  padding-right: 2.25rem;
}
@media (hover: hover) {
  .field select:hover,
  .field input[type="number"]:hover {
    border-color: var(--accent);
  }
}
.field select:focus,
.field input[type="number"]:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--focus-ring);
}

.stepper {
  display: flex;
  align-items: stretch;
  background: var(--surface-muted);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition:
    border-color var(--transition),
    box-shadow var(--transition);
}
@media (hover: hover) {
  .stepper:hover {
    border-color: var(--accent);
  }
}
.stepper:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--focus-ring);
}
.stepper input[type="number"] {
  flex: 1;
  min-width: 0;
  width: auto;
  border: none;
  background: transparent;
  border-radius: 0;
  text-align: center;
  padding: var(--space-3) var(--space-2);
  -moz-appearance: textfield;
  appearance: textfield;
}
.stepper input[type="number"]:focus {
  border-color: transparent;
  box-shadow: none;
}
@media (hover: hover) {
  .stepper input[type="number"]:hover {
    border-color: transparent;
    box-shadow: none;
  }
}
.stepper input[type="number"]::-webkit-inner-spin-button,
.stepper input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.stepper-btn {
  flex: 0 0 auto;
  width: 2.5rem;
  padding: 0;
  background: transparent;
  border: none;
  color: var(--text-muted);
  font: inherit;
  font-size: 1.15rem;
  line-height: 1;
  cursor: pointer;
  transition:
    background-color var(--transition),
    color var(--transition);
}
@media (hover: hover) {
  .stepper-btn:hover:not(:disabled) {
    background: var(--surface);
    color: var(--text);
  }
}
.stepper-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}
.stepper-btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: -2px;
}

@media (max-width: 480px) {
  .container,
  .site-header {
    padding-inline: var(--space-4);
  }
  .result-panel {
    padding: var(--space-5) var(--space-3);
  }
  .card {
    padding: var(--space-4);
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}