:root {
  --brand: #4f46e5;
  --brand-dark: #4338ca;
  --ink: #0f172a;
  --ink-soft: #475569;
  --border: #e2e8f0;
  --bg: #ffffff;
  --bg-alt: #f8fafc;
  --panel: #ffffff;
  --radius: 12px;
  --shadow: 0 1px 2px rgba(15, 23, 42, 0.06), 0 8px 24px rgba(15, 23, 42, 0.06);
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #f1f5f9;
    --ink-soft: #94a3b8;
    --border: #263042;
    --bg: #0b1120;
    --bg-alt: #0f172a;
    --panel: #111a2e;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 8px 24px rgba(0, 0, 0, 0.35);
  }
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.55;
}

img {
  max-width: 100%;
  display: block;
}

.wrap {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 20px;
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--brand);
  color: #fff;
  padding: 10px 16px;
  border-radius: 0 0 8px 0;
  z-index: 100;
}
.skip-link:focus {
  left: 0;
}

/* Header */
.site-header {
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: var(--bg);
  z-index: 10;
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 14px;
  padding-bottom: 14px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--ink);
  text-decoration: none;
}
.site-nav {
  display: flex;
  gap: 24px;
}
.site-nav a {
  color: var(--ink-soft);
  text-decoration: none;
  font-size: 0.95rem;
}
.site-nav a:hover {
  color: var(--brand);
}

/* Hero */
.hero {
  padding: 56px 0 32px;
  text-align: center;
}
.hero h1 {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  margin: 0 0 14px;
  letter-spacing: -0.02em;
}
.hero-sub {
  max-width: 620px;
  margin: 0 auto;
  color: var(--ink-soft);
  font-size: 1.05rem;
}

/* Tool */
.tool {
  padding: 24px 0 64px;
}
.tool-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
  align-items: start;
}
@media (max-width: 760px) {
  .tool-grid {
    grid-template-columns: 1fr;
  }
}

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.field {
  margin-bottom: 18px;
}
.field label {
  display: block;
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 6px;
}
.field-optional {
  font-weight: 400;
  color: var(--ink-soft);
}
.field-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

input[type="text"],
select {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  background: var(--bg);
  color: var(--ink);
}
input[type="text"]:focus,
select:focus {
  outline: 2px solid var(--brand);
  outline-offset: 1px;
}
input[type="color"] {
  width: 100%;
  height: 42px;
  padding: 2px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  cursor: pointer;
}

.field-hint {
  min-height: 1.1em;
  font-size: 0.82rem;
  color: #dc2626;
  margin: 6px 0 0;
}

/* Preview */
.preview-panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
}
.preview-frame {
  width: 100%;
  min-height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: repeating-conic-gradient(#00000008 0% 25%, transparent 0% 50%) 50% / 20px 20px;
  border-radius: 8px;
  margin-bottom: 18px;
  padding: 16px;
  box-sizing: border-box;
}
#qr-canvas {
  max-width: 100%;
  height: auto;
}
.preview-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: center;
}

.btn {
  border: none;
  border-radius: 8px;
  padding: 11px 20px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
}
.btn-primary {
  background: var(--brand);
  color: #fff;
}
.btn-primary:hover {
  background: var(--brand-dark);
}
.btn-secondary {
  background: transparent;
  color: var(--brand);
  border: 1px solid var(--brand);
}
.btn-secondary:hover {
  background: color-mix(in srgb, var(--brand) 10%, transparent);
}

.privacy-note {
  margin: 16px 0 0;
  font-size: 0.85rem;
  color: var(--ink-soft);
}

/* How it works */
.how-it-works {
  padding: 48px 0;
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}
.how-it-works h2,
.features h2,
.faq h2 {
  text-align: center;
  font-size: 1.7rem;
  margin: 0 0 32px;
}
.steps {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
@media (max-width: 760px) {
  .steps {
    grid-template-columns: 1fr;
  }
}
.steps li {
  text-align: center;
}
.step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--brand);
  color: #fff;
  font-weight: 700;
  margin-bottom: 12px;
}
.steps h3 {
  margin: 0 0 6px;
}
.steps p {
  color: var(--ink-soft);
  margin: 0;
}

/* Features */
.features {
  padding: 56px 0;
}
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
@media (max-width: 760px) {
  .feature-grid {
    grid-template-columns: 1fr;
  }
}
.feature-card {
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--panel);
}
.feature-card h3 {
  margin: 0 0 8px;
  font-size: 1.05rem;
}
.feature-card p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 0.95rem;
}

/* FAQ */
.faq {
  padding: 48px 0 72px;
  background: var(--bg-alt);
  border-top: 1px solid var(--border);
}
.faq-list {
  max-width: 720px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.faq-list details {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px 18px;
}
.faq-list summary {
  cursor: pointer;
  font-weight: 600;
}
.faq-list p {
  color: var(--ink-soft);
  margin: 10px 0 0;
}

/* Footer */
.site-footer {
  padding: 28px 0;
  text-align: center;
  color: var(--ink-soft);
  font-size: 0.88rem;
}