/* ============================================
   ABCQR.com - Minimalist QR Code Generator
   CSS Design System (~5KB target)
   ============================================ */

/* --- CSS Variables --- */
:root {
  --color-primary: #43bab7;
  --color-primary-dark: #35948f;
  --color-primary-light: #6dd0cd;
  --color-bg: #ffffff;
  --color-bg-alt: #f7f9fa;
  --color-surface: #ffffff;
  --color-border: #e2e8f0;
  --color-text: #1a202c;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-error: #ef4444;
  --color-success: #22c55e;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', monospace;
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --max-width: 720px;
  --transition: 150ms ease;
}

/* --- Dark Mode --- */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0f172a;
    --color-bg-alt: #1e293b;
    --color-surface: #1e293b;
    --color-border: #334155;
    --color-text: #f1f5f9;
    --color-text-secondary: #94a3b8;
    --color-text-muted: #64748b;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.2);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.3);
    --shadow-lg: 0 8px 24px rgba(0,0,0,0.4);
  }
}

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

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

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

img, svg { display: block; max-width: 100%; }
a { color: var(--color-primary); text-decoration: none; }
a:hover { color: var(--color-primary-dark); }

/* --- Layout --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

main { flex: 1; }

/* --- Header --- */
.header {
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--color-border);
}

.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.header__logo {
  height: 32px;
  width: auto;
}

.header__right {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.header__nav {
  display: flex;
  gap: var(--space-md);
  list-style: none;
}

.header__nav a {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: color var(--transition);
}

.header__nav a:hover { color: var(--color-primary); }

.lang-switch {
  position: relative;
}

.lang-select {
  appearance: none;
  -webkit-appearance: none;
  padding: var(--space-xs) var(--space-xl) var(--space-xs) var(--space-sm);
  font-size: 0.85rem;
  font-family: var(--font-sans);
  font-weight: 500;
  color: var(--color-text-secondary);
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  outline: none;
  transition: border-color var(--transition), color var(--transition);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2364748b' stroke-width='2'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 8px center;
}

.lang-select:hover,
.lang-select:focus {
  border-color: var(--color-primary);
  color: var(--color-text);
}

/* --- Hero --- */
.hero {
  text-align: center;
  padding: var(--space-2xl) 0 var(--space-xl);
}

.hero h1 {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: var(--space-sm);
}

.hero p {
  color: var(--color-text-secondary);
  font-size: 1.1rem;
}

/* --- Generator Card --- */
.generator {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  margin-bottom: var(--space-3xl);
}

/* Tabs */
.tabs {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg-alt);
}

.tab {
  padding: var(--space-sm) var(--space-xs);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: color var(--transition), border-color var(--transition), background var(--transition);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  white-space: nowrap;
  font-family: var(--font-sans);
}

.tab:hover {
  color: var(--color-text);
  background: var(--color-surface);
}

.tab.active {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
  background: var(--color-surface);
}

.tab__icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 18px;
  height: 18px;
}

.tab__icon svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

/* Form Area */
.form-area {
  padding: var(--space-xl);
}

.field {
  margin-bottom: var(--space-md);
}

.field label {
  display: block;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xs);
}

.field input,
.field textarea,
.field select {
  width: 100%;
  padding: var(--space-sm) var(--space-md);
  font-size: 0.95rem;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  transition: border-color var(--transition), box-shadow var(--transition);
  outline: none;
}

.field input:focus,
.field textarea:focus,
.field select:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(67, 186, 183, 0.15);
}

.field textarea {
  resize: vertical;
  min-height: 80px;
}

.field select {
  cursor: pointer;
}

.field-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-md);
}

/* Output Area */
.output-area {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--space-xl);
  padding-top: 0;
  gap: var(--space-lg);
}

.qr-preview {
  background: #fff;
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
}

.qr-preview canvas {
  display: block;
}

.qr-placeholder {
  width: 200px;
  height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  font-size: 0.85rem;
  text-align: center;
}

.download-buttons {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
  justify-content: center;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-sm) var(--space-lg);
  font-size: 0.9rem;
  font-weight: 500;
  font-family: var(--font-sans);
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), box-shadow var(--transition);
}

.btn-primary {
  background: var(--color-primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  box-shadow: var(--shadow-sm);
}

.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-outline:hover {
  background: var(--color-primary);
  color: #fff;
}

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

/* Options Panel */
.options-panel {
  padding: 0 var(--space-xl) var(--space-xl);
}

.options-toggle {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm) 0;
  font-family: var(--font-sans);
  transition: color var(--transition);
}

.options-toggle:hover { color: var(--color-text); }

.options-toggle__arrow {
  transition: transform var(--transition);
  font-size: 0.7rem;
}

.options-toggle__arrow.open {
  transform: rotate(90deg);
}

.options-content {
  display: none;
  padding-top: var(--space-md);
}

.options-content.open {
  display: block;
}

.color-input-wrapper {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.color-input-wrapper input[type="color"] {
  width: 40px;
  height: 34px;
  padding: 2px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  background: var(--color-bg);
}

.color-input-wrapper input[type="text"] {
  width: 90px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

.size-options {
  display: flex;
  gap: var(--space-sm);
}

.size-option {
  padding: var(--space-xs) var(--space-md);
  font-size: 0.85rem;
  font-weight: 500;
  font-family: var(--font-sans);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition);
}

.size-option:hover { border-color: var(--color-primary); color: var(--color-primary); }
.size-option.active {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

/* --- Content Sections --- */
.content-section {
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--color-border);
}

.content-section h2 {
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: var(--space-lg);
  letter-spacing: -0.01em;
}

.content-section p {
  color: var(--color-text-secondary);
  margin-bottom: var(--space-md);
  line-height: 1.7;
}

.steps {
  display: grid;
  gap: var(--space-lg);
  counter-reset: step;
}

.step {
  display: flex;
  gap: var(--space-lg);
  align-items: flex-start;
}

.step__number {
  flex: 0 0 auto;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--color-primary);
  color: #fff;
  font-weight: 600;
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.step__content h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.step__content p {
  font-size: 0.9rem;
  margin-bottom: 0;
}

/* FAQ */
.faq-list {
  display: grid;
  gap: var(--space-sm);
}

.faq-item {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.faq-question {
  width: 100%;
  padding: var(--space-md) var(--space-lg);
  font-size: 0.95rem;
  font-weight: 500;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg-alt);
  border: none;
  cursor: pointer;
  text-align: left;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background var(--transition);
}

.faq-question:hover { background: var(--color-border); }

.faq-question::after {
  content: '+';
  font-size: 1.2rem;
  color: var(--color-text-muted);
  transition: transform var(--transition);
}

.faq-item.open .faq-question::after {
  content: '−';
}

.faq-answer {
  display: none;
  padding: var(--space-md) var(--space-lg);
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.7;
}

.faq-item.open .faq-answer {
  display: block;
}

/* --- Footer --- */
.footer {
  padding: var(--space-xl) 0;
  border-top: 1px solid var(--color-border);
  margin-top: auto;
}

.footer .container {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-xs);
}

.footer__copy {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.footer__meta {
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

.footer__meta a {
  color: var(--color-text-secondary);
}

.footer__heart {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  margin-top: var(--space-xs);
}

.footer__links {
  display: flex;
  gap: var(--space-lg);
  list-style: none;
  margin-top: var(--space-sm);
}

.footer__links a {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  transition: color var(--transition);
}

.footer__links a:hover { color: var(--color-primary); }

/* --- Responsive --- */
@media (max-width: 640px) {
  .header__right { gap: var(--space-sm); }
  .header__nav { gap: var(--space-sm); }
  .header__nav a { font-size: 0.8rem; }
  .hero h1 { font-size: 1.5rem; }
  .hero p { font-size: 1rem; }
  .form-area { padding: var(--space-lg); }
  .output-area { padding: var(--space-lg); padding-top: 0; }
  .options-panel { padding: 0 var(--space-lg) var(--space-lg); }
  .field-row { grid-template-columns: 1fr; }
  .tabs { grid-template-columns: repeat(5, 1fr); }
  .tab { padding: var(--space-xs) 2px; font-size: 0.65rem; }
  .tab__icon svg { width: 16px; height: 16px; }
  .tab__icon { width: 16px; height: 16px; }
  .step { flex-direction: column; gap: var(--space-sm); }
  .footer .container { flex-direction: column; text-align: center; }
}

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

.hidden { display: none !important; }