/* =============================================================================
   Hedron Contrast Checker — style.css
   Font: Source Sans 3 (updated Source Sans Pro by Adobe, via Google Fonts)
   ============================================================================= */

/* =============================================================================
   1. CSS Custom Properties
   ============================================================================= */

:root {
  /* Tipografia */
  --font-sans: 'Source Sans 3', 'Source Sans Pro', system-ui, -apple-system, sans-serif;
  --font-mono: 'Source Code Pro', 'Fira Code', 'Cascadia Code', monospace;

  /* Scala tipografica */
  --text-xs:   0.75rem;   /* 12px */
  --text-sm:   0.875rem;  /* 14px */
  --text-base: 1rem;      /* 16px */
  --text-lg:   1.125rem;  /* 18px */
  --text-xl:   1.25rem;   /* 20px */
  --text-2xl:  1.5rem;    /* 24px */
  --text-3xl:  1.875rem;  /* 30px */

  /* Pesi */
  --weight-light:   300;
  --weight-regular: 400;
  --weight-medium:  500;
  --weight-semi:    600;

  /* Spacing */
  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-5:  1.25rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;

  /* Border radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  /* Colori — Light mode */
  --color-bg:            #f4f4f0;
  --color-surface:       #ffffff;
  --color-surface-alt:   #f9f9f6;
  --color-border:        rgba(0, 0, 0, 0.09);
  --color-border-strong: rgba(0, 0, 0, 0.18);
  --color-border-focus:  #2563eb;

  --color-text:          #1c1c1a;
  --color-text-2:        #515149;
  --color-text-3:        #909088;
  --color-text-inverse:  #ffffff;

  --color-accent:        #2563eb;
  --color-accent-light:  rgba(37, 99, 235, 0.10);
  --color-accent-hover:  #1d4ed8;

  /* Semantici */
  --color-pass:          #15803d;
  --color-pass-bg:       #f0fdf4;
  --color-pass-border:   #bbf7d0;

  --color-warn:          #92400e;
  --color-warn-bg:       #fefce8;
  --color-warn-border:   #fde68a;

  --color-fail:          #b91c1c;
  --color-fail-bg:       #fef2f2;
  --color-fail-border:   #fecaca;

  --color-info:          #1e40af;
  --color-info-bg:       #eff6ff;
  --color-info-border:   #bfdbfe;

  /* Transizioni */
  --transition-fast: 120ms ease;
  --transition-base: 200ms ease;

  /* Layout */
  --max-width: 900px;
  --header-height: 72px;
}

/* Dark mode */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg:            #111110;
    --color-surface:       #1e1e1c;
    --color-surface-alt:   #252523;
    --color-border:        rgba(255, 255, 255, 0.08);
    --color-border-strong: rgba(255, 255, 255, 0.16);

    --color-text:          #eeeee8;
    --color-text-2:        #a8a89e;
    --color-text-3:        #5a5a54;

    --color-accent:        #60a5fa;
    --color-accent-light:  rgba(96, 165, 250, 0.12);
    --color-accent-hover:  #93c5fd;

    --color-pass:          #4ade80;
    --color-pass-bg:       rgba(74, 222, 128, 0.08);
    --color-pass-border:   rgba(74, 222, 128, 0.22);

    --color-warn:          #fcd34d;
    --color-warn-bg:       rgba(252, 211, 77, 0.08);
    --color-warn-border:   rgba(252, 211, 77, 0.22);

    --color-fail:          #f87171;
    --color-fail-bg:       rgba(248, 113, 113, 0.08);
    --color-fail-border:   rgba(248, 113, 113, 0.22);

    --color-info:          #93c5fd;
    --color-info-bg:       rgba(147, 197, 253, 0.08);
    --color-info-border:   rgba(147, 197, 253, 0.22);
  }
}


/* =============================================================================
   2. Reset & base
   ============================================================================= */

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  font-weight: var(--weight-regular);
  font-size: var(--text-base);
  line-height: 1.65;
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
}

h1, h2, h3 {
  font-weight: var(--weight-semi);
  line-height: 1.25;
  color: var(--color-text);
}

a {
  color: var(--color-accent);
  text-decoration: underline;
  text-underline-offset: 2px;
  transition: color var(--transition-fast);
}

a:hover  { color: var(--color-accent-hover); }
a:focus-visible {
  outline: 2px solid var(--color-border-focus);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

p { max-width: 72ch; }

strong { font-weight: var(--weight-semi); }


/* =============================================================================
   3. Accessibility — utilities
   ============================================================================= */

/* Visually hidden: available to screen readers, invisible to sighted users */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* Skip link — keyboard navigation */
.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-4);
  z-index: 100;
  padding: var(--space-2) var(--space-4);
  background: var(--color-surface);
  border: 2px solid var(--color-border-focus);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  color: var(--color-accent);
  text-decoration: none;
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: var(--space-3);
}

/* Global focus ring for interactive elements */
:focus-visible {
  outline: 2px solid var(--color-border-focus);
  outline-offset: 2px;
}


/* =============================================================================
   4. Page layout
   ============================================================================= */

.page-wrapper {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  padding: 0 var(--space-4);
}

.main-content {
  flex: 1;
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-6) 0 var(--space-12);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}


/* =============================================================================
   5. Site header
   ============================================================================= */

.site-header {
  width: 100%;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-surface);
  margin-bottom: var(--space-2);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-5) 0;
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.brand {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
}

.brand-name {
  font-size: var(--text-xl);
  font-weight: var(--weight-semi);
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.brand-tool {
  font-size: var(--text-xl);
  font-weight: var(--weight-light);
  color: var(--color-text-2);
}

.header-description {
  font-size: var(--text-sm);
  color: var(--color-text-2);
  line-height: 1.5;
}


/* =============================================================================
   6. Color input section
   ============================================================================= */

.input-section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
}

.color-inputs-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: var(--space-4);
  align-items: center;
}

@media (max-width: 580px) {
  .color-inputs-grid {
    grid-template-columns: 1fr;
  }
  .swap-col {
    display: flex;
    justify-content: center;
  }
}

/* Fieldset reset */
.color-fieldset {
  border: none;
  padding: 0;
  min-width: 0;
}

.fieldset-legend {
  font-size: var(--text-xs);
  font-weight: var(--weight-semi);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--color-text-3);
  margin-bottom: var(--space-3);
  float: left;
  width: 100%;
}

/* Picker + hex row */
.picker-hex-row {
  display: flex;
  align-items: flex-end;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
  clear: both;
}

.picker-wrap {
  flex-shrink: 0;
}

input[type="color"] {
  display: block;
  width: 42px;
  height: 42px;
  padding: 3px;
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius-md);
  background: none;
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

input[type="color"]:hover {
  border-color: var(--color-accent);
}

input[type="color"]:focus-visible {
  outline: 2px solid var(--color-border-focus);
  outline-offset: 2px;
}

/* Hex text input */
.hex-wrap {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.input-label {
  font-size: var(--text-xs);
  font-weight: var(--weight-semi);
  color: var(--color-text-3);
  letter-spacing: 0.05em;
}

.hex-input {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  padding: 8px 10px;
  width: 110px;
  background: var(--color-surface-alt);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  text-transform: uppercase;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.hex-input:hover { border-color: var(--color-border-strong); }

.hex-input:focus {
  outline: none;
  border-color: var(--color-border-focus);
  box-shadow: 0 0 0 3px var(--color-accent-light);
}

.hex-input.invalid {
  border-color: var(--color-fail);
  box-shadow: 0 0 0 3px var(--color-fail-bg);
}

/* RGB inputs */
.rgb-row {
  display: flex;
  gap: var(--space-2);
}

.rgb-channel {
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
  align-items: center;
}

.rgb-label {
  font-size: var(--text-xs);
  font-weight: var(--weight-semi);
  color: var(--color-text-3);
  letter-spacing: 0.04em;
}

.rgb-input {
  width: 60px;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  padding: 7px 4px;
  background: var(--color-surface-alt);
  color: var(--color-text);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  text-align: center;
  -moz-appearance: textfield;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.rgb-input::-webkit-outer-spin-button,
.rgb-input::-webkit-inner-spin-button { -webkit-appearance: none; }

.rgb-input:hover  { border-color: var(--color-border-strong); }

.rgb-input:focus {
  outline: none;
  border-color: var(--color-border-focus);
  box-shadow: 0 0 0 3px var(--color-accent-light);
}

/* Swap colors button */
.swap-col {
  display: flex;
  justify-content: center;
  align-items: center;
}

.swap-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border: 1px solid var(--color-border);
  border-radius: 50%;
  background: var(--color-surface);
  color: var(--color-text-3);
  cursor: pointer;
  transition: background var(--transition-fast), border-color var(--transition-fast), color var(--transition-fast), transform var(--transition-fast);
}

.swap-btn:hover {
  background: var(--color-accent-light);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.swap-btn:active {
  transform: rotate(180deg);
}

.swap-btn:focus-visible {
  outline: 2px solid var(--color-border-focus);
  outline-offset: 2px;
}


/* =============================================================================
   7. Text preview
   ============================================================================= */

.preview-section {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-border);
}

.preview-box {
  padding: var(--space-8) var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  align-items: center;
  justify-content: center;
  min-height: 120px;
  transition: background var(--transition-base);
}

.preview-normal {
  font-size: var(--text-base);
  font-weight: var(--weight-regular);
  text-align: center;
  line-height: 1.5;
  max-width: none;
  transition: color var(--transition-base);
}

.preview-large {
  font-size: var(--text-2xl);
  font-weight: var(--weight-semi);
  text-align: center;
  max-width: none;
  transition: color var(--transition-base);
}


/* =============================================================================
   8. Metrics
   ============================================================================= */

.results-section {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.metrics-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
}

@media (max-width: 500px) {
  .metrics-grid { grid-template-columns: 1fr; }
}

.metric-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
}

.metric-header {
  margin-bottom: var(--space-2);
}

.metric-standard {
  display: block;
  font-size: var(--text-xs);
  font-weight: var(--weight-semi);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-text-3);
}

.metric-description {
  display: block;
  font-size: var(--text-xs);
  color: var(--color-text-3);
  margin-top: 1px;
}

.metric-value {
  font-size: var(--text-3xl);
  font-weight: var(--weight-semi);
  font-variant-numeric: tabular-nums;
  line-height: 1;
  margin-bottom: var(--space-3);
  color: var(--color-text);
  letter-spacing: -0.02em;
}

/* Level badges */
.metric-badges {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: var(--text-xs);
  font-weight: var(--weight-medium);
  padding: 3px 9px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  line-height: 1.4;
}

.badge-pass   { background: var(--color-pass-bg);   color: var(--color-pass);   border-color: var(--color-pass-border); }
.badge-fail   { background: var(--color-fail-bg);   color: var(--color-fail);   border-color: var(--color-fail-border); }
.badge-warn   { background: var(--color-warn-bg);   color: var(--color-warn);   border-color: var(--color-warn-border); }

/* Algorithm divergence note */
.divergence-note {
  background: var(--color-warn-bg);
  border: 1px solid var(--color-warn-border);
  border-radius: var(--radius-md);
  padding: var(--space-3) var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-warn);
  line-height: 1.6;
}

.divergence-note[hidden] { display: none; }


/* =============================================================================
   9. Conformant variants
   ============================================================================= */

.suggestions-section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
}

.section-header {
  margin-bottom: var(--space-4);
}

.section-title {
  font-size: var(--text-lg);
  font-weight: var(--weight-semi);
  margin-bottom: var(--space-1);
}

.section-description {
  font-size: var(--text-sm);
  color: var(--color-text-2);
  line-height: 1.5;
}

/* Suggestion groups */
.suggestion-group {
  margin-bottom: var(--space-5);
}

.suggestion-group:last-child {
  margin-bottom: 0;
}

.group-label {
  font-size: var(--text-xs);
  font-weight: var(--weight-semi);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--color-text-3);
  margin-bottom: var(--space-3);
}

.swatches-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* Swatch: <button> for keyboard accessibility */
.swatch-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2);
  width: 100px;
  background: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast);
  text-align: center;
  color: var(--color-text);
}

.swatch-btn:hover {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-light);
  background: var(--color-surface);
}

.swatch-btn:focus-visible {
  outline: 2px solid var(--color-border-focus);
  outline-offset: 2px;
}

.swatch-preview {
  display: block;
  width: 68px;
  height: 44px;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(128, 128, 128, 0.15);
  flex-shrink: 0;
}

.swatch-hex {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-text-2);
  letter-spacing: 0.02em;
}

.swatch-ratio {
  font-size: var(--text-xs);
  color: var(--color-text-3);
}

.swatch-badges {
  display: flex;
  flex-wrap: wrap;
  gap: 3px;
  justify-content: center;
}

.swatch-badge {
  font-size: 9px;
  font-weight: var(--weight-semi);
  padding: 1px 5px;
  border-radius: 3px;
  border: 1px solid transparent;
  line-height: 1.5;
}

/* Empty state */
.no-suggestions {
  font-size: var(--text-sm);
  color: var(--color-text-3);
  padding: var(--space-2) 0;
}


/* =============================================================================
   10. Reference table
   ============================================================================= */

.reference-section {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
}

.reference-section .section-title {
  margin-bottom: var(--space-4);
}

.table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.reference-table {
  width: 100%;
  border-collapse: collapse;
  font-size: var(--text-sm);
}

.reference-table caption {
  text-align: left;
  font-size: var(--text-xs);
  color: var(--color-text-3);
  margin-bottom: var(--space-2);
}

.reference-table th {
  text-align: left;
  font-weight: var(--weight-medium);
  font-size: var(--text-xs);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-3);
  padding: var(--space-2) var(--space-3) var(--space-2) 0;
  border-bottom: 1px solid var(--color-border);
  white-space: nowrap;
}

.reference-table td {
  padding: var(--space-2) var(--space-3) var(--space-2) 0;
  border-bottom: 1px solid var(--color-border);
  color: var(--color-text-2);
  vertical-align: middle;
}

.reference-table tr:last-child td {
  border-bottom: none;
}

.reference-table td:first-child {
  font-weight: var(--weight-medium);
  color: var(--color-text);
  white-space: nowrap;
}

.reference-table td:nth-child(2) {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  white-space: nowrap;
  padding-right: var(--space-6);
}


/* =============================================================================
   11. Site footer
   ============================================================================= */

.site-footer {
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
  margin-top: auto;
}

.site-footer > * {
  max-width: var(--max-width);
  margin: 0 auto;
}

.site-footer p {
  padding: var(--space-4) 0;
  font-size: var(--text-xs);
  color: var(--color-text-3);
  line-height: 1.7;
  max-width: none;
}

.site-footer p + p {
  border-top: 1px solid var(--color-border);
}


/* =============================================================================
   12. Print styles
   ============================================================================= */

@media print {
  .skip-link,
  .swap-btn,
  .input-section,
  .preview-section,
  .suggestions-section {
    display: none;
  }

  .site-header,
  .metric-card,
  .reference-section {
    border: 1px solid #ccc;
    box-shadow: none;
  }

  body {
    background: white;
    color: black;
  }
}