:root {
  --bg: #f8fafc;
  --bg-subtle: #f1f5f9;
  --card-bg: #ffffff;
  --card-border: #e2e8f0;
  --card-hover-border: #cbd5e1;
  --inner-border: #e2e8f0;
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-subtle: #94a3b8;
  --primary: #0f172a;
  --primary-hover: #1e293b;
  --primary-light: #f1f5f9;
  --primary-ring: rgba(15, 23, 42, 0.1);
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --shadow-card: 0 1px 3px 0 rgba(0, 0, 0, 0.05), 0 1px 2px -1px rgba(0, 0, 0, 0.05);
}

[data-theme="dark"] {
  --bg: #090d16;
  --bg-subtle: #131b2e;
  --card-bg: #0f172a;
  --card-border: #1e293b;
  --card-hover-border: #334155;
  --inner-border: #1e293b;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-subtle: #64748b;
  --primary: #f8fafc;
  --primary-hover: #e2e8f0;
  --primary-light: #1e293b;
  --primary-ring: rgba(248, 250, 252, 0.15);
  --shadow-card: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background-color: var(--bg);
  color: var(--text-main);
  min-height: 100vh;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  padding-bottom: 40px;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Header */
header {
  padding: 24px 0 16px;
}

.nav-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: inherit;
}

.brand-icon {
  width: 32px;
  height: 32px;
  background: var(--text-main);
  color: var(--bg);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  font-weight: 700;
}

[data-theme="dark"] .brand-icon {
  background: #f8fafc;
  color: #090d16;
}

.brand-text h1 {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.2;
}

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

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.icon-btn {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-muted);
  width: 34px;
  height: 34px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 14px;
  transition: all 0.15s ease;
}

.icon-btn:hover {
  color: var(--text-main);
  border-color: var(--card-hover-border);
  background: var(--primary-light);
}

.lang-btn {
  padding: 0 10px;
  width: auto;
  font-size: 0.8rem;
  font-weight: 500;
}

/* Main Grid: Structured Two-Column Cards */
.main-grid {
  display: grid;
  grid-template-columns: 1fr 340px;
  gap: 20px;
  align-items: start;
}

@media (max-width: 820px) {
  .main-grid {
    grid-template-columns: 1fr;
  }
}

/* Card base */
.card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  padding: 22px;
  box-shadow: var(--shadow-card);
}

/* Editor Card */
.editor-card {
  display: flex;
  flex-direction: column;
}

/* Tabs: Segmented Control Frame */
.tabs-nav {
  display: flex;
  gap: 4px;
  background: var(--bg-subtle);
  border: 1px solid var(--card-border);
  padding: 4px;
  border-radius: var(--radius-md);
  margin-bottom: 18px;
}

.tab-btn {
  flex: 1;
  padding: 7px 10px;
  font-size: 0.84rem;
  font-weight: 500;
  color: var(--text-muted);
  background: transparent;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: all 0.15s ease;
}

.tab-btn:hover {
  color: var(--text-main);
}

.tab-btn.active {
  background: var(--card-bg);
  color: var(--text-main);
  font-weight: 600;
  box-shadow: 0 1px 2px rgba(0,0,0,0.06);
  border: 1px solid var(--card-border);
}

/* Form inputs & Label rows */
.form-group {
  margin-bottom: 14px;
}

.form-label-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 6px;
}

.form-label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-main);
}

.btn-text-action {
  background: var(--bg-subtle);
  border: 1px solid var(--card-border);
  color: var(--text-muted);
  font-size: 0.78rem;
  cursor: pointer;
  padding: 3px 8px;
  border-radius: 4px;
  transition: all 0.15s ease;
}

.btn-text-action:hover {
  color: var(--text-main);
  border-color: var(--card-hover-border);
  background: var(--card-bg);
}

.btn-clean-inline {
  color: #2563eb;
  border-color: rgba(37, 99, 235, 0.25);
  background: rgba(37, 99, 235, 0.05);
}

.btn-clean-inline:hover {
  background: rgba(37, 99, 235, 0.12);
  border-color: rgba(37, 99, 235, 0.4);
}

.input-actions-inline {
  display: flex;
  align-items: center;
  gap: 6px;
}

.form-control {
  width: 100%;
  padding: 10px 14px;
  font-size: 0.92rem;
  font-family: inherit;
  color: var(--text-main);
  background: var(--bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  outline: none;
  transition: all 0.15s ease;
}

.form-control:focus {
  border-color: #3b82f6;
  box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.15);
  background: var(--card-bg);
}

textarea.form-control {
  resize: vertical;
  min-height: 100px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

/* Customization Accordions: Structured framed boxes */
.customization-section {
  margin-top: 10px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.accordion {
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  background: var(--card-bg);
  overflow: hidden;
  transition: border-color 0.15s ease;
}

.accordion:hover {
  border-color: var(--card-hover-border);
}

.accordion-header {
  padding: 9px 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  user-select: none;
  background: var(--bg);
  transition: background 0.15s ease;
}

.accordion-header:hover {
  background: var(--bg-subtle);
}

.accordion-title {
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-muted);
}

.accordion-header:hover .accordion-title {
  color: var(--text-main);
}

.accordion-chevron {
  font-size: 0.68rem;
  color: var(--text-subtle);
  transition: transform 0.2s ease;
}

.accordion.open .accordion-chevron {
  transform: rotate(180deg);
}

.accordion-body {
  padding: 14px;
  display: none;
  border-top: 1px solid var(--card-border);
  background: var(--card-bg);
}

.accordion.open .accordion-body {
  display: block;
}

/* Style options */
.style-options {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 6px;
}

.style-option-btn {
  padding: 7px;
  text-align: center;
  border: 1px solid var(--card-border);
  background: var(--bg);
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  font-weight: 500;
  cursor: pointer;
  color: var(--text-muted);
  transition: all 0.15s ease;
}

.style-option-btn:hover {
  color: var(--text-main);
  border-color: var(--card-hover-border);
}

.style-option-btn.active {
  border-color: var(--text-main);
  color: var(--text-main);
  background: var(--primary-light);
  font-weight: 600;
}

/* Color palettes */
.palette-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
  flex-wrap: wrap;
}

.color-swatch {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  cursor: pointer;
  border: 2px solid #ffffff;
  box-shadow: 0 0 0 1px var(--card-border);
  transition: transform 0.15s ease;
}

.color-swatch:hover {
  transform: scale(1.15);
}

.color-swatch.active {
  box-shadow: 0 0 0 2px var(--text-main);
}

.color-picker-input {
  width: 32px;
  height: 32px;
  padding: 0;
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  background: transparent;
}

.slider-container {
  display: flex;
  align-items: center;
  gap: 12px;
}

.slider-container input[type="range"] {
  flex: 1;
  accent-color: var(--text-main);
}

.slider-val {
  min-width: 28px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-align: right;
}

/* Preview Card */
.preview-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  position: sticky;
  top: 20px;
}

/* Canvas Box Frame */
.canvas-wrapper {
  width: 250px;
  height: 250px;
  background: #ffffff;
  border-radius: var(--radius-md);
  padding: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--inner-border);
  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
  margin-bottom: 12px;
  position: relative;
  overflow: hidden;
}

.canvas-wrapper.transparent-bg {
  background-image: 
    linear-gradient(45deg, #f1f5f9 25%, transparent 25%),
    linear-gradient(-45deg, #f1f5f9 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, #f1f5f9 75%),
    linear-gradient(-45deg, transparent 75%, #f1f5f9 75%);
  background-size: 14px 14px;
  background-position: 0 0, 0 7px, 7px -7px, -7px 0px;
}

#qrCanvas {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  display: block;
}

.preview-status {
  font-size: 0.75rem;
  color: var(--text-subtle);
  margin-bottom: 12px;
}

.size-selector {
  width: 100%;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.size-select-input {
  padding: 5px 8px;
  border: 1px solid var(--card-border);
  background: var(--bg);
  border-radius: var(--radius-sm);
  color: var(--text-main);
  font-size: 0.8rem;
  outline: none;
}

/* Action buttons */
.action-buttons {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.btn-primary {
  width: 100%;
  padding: 10px 16px;
  background: var(--text-main);
  color: var(--bg);
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
  transition: opacity 0.15s ease;
}

[data-theme="dark"] .btn-primary {
  background: #f8fafc;
  color: #090d16;
}

.btn-primary:hover {
  opacity: 0.9;
}

.button-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  width: 100%;
}

.btn-secondary {
  width: 100%;
  padding: 8px 12px;
  background: var(--card-bg);
  color: var(--text-main);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  transition: all 0.15s ease;
}

.btn-secondary:hover {
  border-color: var(--card-hover-border);
  background: var(--bg);
}

/* Bookmark & User Retention Card */
.bookmark-card {
  width: 100%;
  margin-top: 16px;
  padding: 12px 14px;
  background: var(--bg-subtle);
  border: 1px dashed var(--card-border);
  border-radius: var(--radius-md);
  text-align: left;
}

.bookmark-header {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 4px;
}

.bookmark-icon {
  font-size: 14px;
}

.bookmark-title {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-main);
}

.kbd-key {
  display: inline-block;
  padding: 1px 5px;
  font-size: 0.72rem;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  color: var(--text-main);
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 4px;
  box-shadow: 0 1px 0 rgba(0,0,0,0.1);
}

.bookmark-desc {
  font-size: 0.74rem;
  color: var(--text-muted);
  line-height: 1.4;
  margin-bottom: 8px;
}

.btn-bookmark-action {
  width: 100%;
  padding: 6px 10px;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-main);
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  transition: all 0.15s ease;
}

.btn-bookmark-action:hover {
  border-color: var(--card-hover-border);
  background: var(--bg);
}

/* Toast */
.toast-container {
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: 6px;
  pointer-events: none;
}

.toast {
  background: #0f172a;
  color: #ffffff;
  padding: 9px 16px;
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  font-weight: 500;
  box-shadow: 0 4px 12px rgba(0,0,0,0.18);
  display: flex;
  align-items: center;
  gap: 6px;
  opacity: 0;
  transform: translateY(8px);
  transition: all 0.2s ease;
}

.toast.show {
  opacity: 1;
  transform: translateY(0);
}