/* ===========================
   WebTool.kr — Design System
   =========================== */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Pretendard+Variable:wght@400;500;600;700&display=swap');

/* --- CSS Variables (Light) --- */
:root {
  /* Colors */
  --color-accent: #3b82f6;
  --color-accent-hover: #2563eb;
  --color-accent-light: rgba(59, 130, 246, 0.1);
  --color-accent-subtle: rgba(59, 130, 246, 0.06);

  --color-bg: #f5f5fa;
  --color-surface: #ffffff;
  --color-surface-hover: #fafafe;
  --color-border: #e2e4ea;
  --color-border-light: #eff0f3;

  --color-text: #1a1c25;
  --color-text-secondary: #5f6368;
  --color-text-tertiary: #9aa0a6;
  --color-text-inverse: #ffffff;

  --color-success: #34a853;
  --color-success-bg: rgba(52, 168, 83, 0.08);
  --color-warning: #f9ab00;
  --color-warning-bg: rgba(249, 171, 0, 0.08);
  --color-error: #ea4335;
  --color-error-bg: rgba(234, 67, 53, 0.08);

  /* Typography */
  --font-family: 'Pretendard Variable', Pretendard, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 2rem;
  --font-size-4xl: 2.5rem;

  /* Spacing (8px grid) */
  --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;
  --space-16: 4rem;
  --space-20: 5rem;

  /* Border radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.08);
  --shadow-xl: 0 12px 40px rgba(0, 0, 0, 0.12);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;

  /* Layout */
  --header-height: 64px;
  --max-width: 1200px;
  --content-width: 800px;
}

/* --- Dark Mode --- */
[data-theme="dark"] {
  --color-bg: #0f1117;
  --color-surface: #1a1c25;
  --color-surface-hover: #22242e;
  --color-border: #2d303a;
  --color-border-light: #24262f;

  --color-text: #e8eaed;
  --color-text-secondary: #9aa0a6;
  --color-text-tertiary: #6b7075;

  --color-accent-light: rgba(59, 130, 246, 0.15);
  --color-accent-subtle: rgba(59, 130, 246, 0.08);

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.35);
  --shadow-xl: 0 12px 40px rgba(0, 0, 0, 0.4);
}

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

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

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-accent-hover);
}

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

button {
  cursor: pointer;
  font-family: inherit;
  font-size: inherit;
  border: none;
  background: none;
}

input, select {
  font-family: inherit;
  font-size: inherit;
}

/* --- Header --- */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-height);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.85);
}

[data-theme="dark"] .header {
  background: rgba(26, 28, 37, 0.85);
}

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

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

.logo-separator {
  color: var(--color-text-tertiary);
  font-weight: 300;
  margin: 0 2px;
  position: relative;
  top: -2px;
}

.logo-sub {
  color: var(--color-accent);
  font-weight: 700;
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.nav-link {
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
  font-size: var(--font-size-sm);
  font-weight: 500;
  transition: all var(--transition-fast);
}

.nav-link:hover {
  color: var(--color-text);
  background: var(--color-accent-subtle);
}

.nav-link.active {
  color: var(--color-accent);
  background: var(--color-accent-light);
}

/* Nav dropdown */
.nav-dropdown {
  position: relative;
}

.nav-dropdown-trigger {
  display: flex;
  align-items: center;
  gap: 4px;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
  font-family: inherit;
  font-size: var(--font-size-sm);
  font-weight: 500;
  background: none;
  border: none;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.nav-dropdown-trigger:hover {
  color: var(--color-text);
  background: var(--color-accent-subtle);
}

.nav-dropdown-trigger svg {
  width: 12px;
  height: 12px;
  transition: transform 0.2s;
}

.nav-dropdown:hover .nav-dropdown-trigger svg {
  transform: rotate(180deg);
}

.nav-dropdown-menu {
  position: absolute;
  top: 100%;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  box-shadow: 0 8px 24px rgba(0,0,0,0.12);
  padding: 6px 0;
  padding-top: 10px;
  min-width: 170px;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.15s;
  z-index: 200;
}

/* Invisible bridge area to prevent hover gap */
.nav-dropdown-menu::before {
  content: '';
  position: absolute;
  top: -8px;
  left: 0;
  right: 0;
  height: 8px;
}

[data-theme="dark"] .nav-dropdown-menu {
  box-shadow: 0 8px 24px rgba(0,0,0,0.4);
}

.nav-dropdown:hover .nav-dropdown-menu {
  opacity: 1;
  visibility: visible;
}

.nav-dropdown-menu a {
  display: block;
  padding: 8px 16px;
  color: var(--color-text);
  text-decoration: none;
  font-size: 0.875rem;
  font-weight: 400;
  transition: background 0.1s, color 0.1s;
}

.nav-dropdown-menu a:hover {
  background: var(--color-accent-subtle);
  color: var(--color-accent);
}

.nav-dropdown-menu a.nav-active {
  color: var(--color-accent);
  font-weight: 600;
}

.mobile-nav .nav-link.nav-active {
  color: var(--color-accent);
  font-weight: 600;
}

/* Mobile menu button */
.menu-btn {
  display: none;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
}

.menu-btn:hover {
  background: var(--color-accent-subtle);
}

/* Theme toggle */
.theme-toggle {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  color: var(--color-text);
  background: var(--color-accent-subtle);
}

.theme-toggle svg {
  width: 20px;
  height: 20px;
}

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

/* Mobile nav overlay */
.mobile-nav {
  display: none;
  position: fixed;
  top: var(--header-height);
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--color-surface);
  z-index: 99;
  padding: var(--space-4) var(--space-6);
  flex-direction: column;
  gap: 0;
  overflow-y: auto;
}

.mobile-nav.open {
  display: flex;
}

.mobile-nav-group {
  display: flex;
  flex-direction: column;
  padding: var(--space-3) 0;
  border-bottom: 1px solid var(--color-border);
}

.mobile-nav-group:last-child {
  border-bottom: none;
}

.mobile-nav-title {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--color-text);
  padding: var(--space-1) var(--space-3);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.mobile-nav .nav-link {
  display: block;
  font-size: var(--font-size-base);
  padding: var(--space-1) var(--space-3);
}

/* --- Main content --- */
.main {
  flex: 1;
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-8) var(--space-6);
}

.main--narrow {
  max-width: var(--content-width);
}

/* --- Hero --- */
.hero {
  text-align: center;
  padding: var(--space-16) 0 var(--space-12);
}

.hero-title {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--space-4);
  letter-spacing: -0.02em;
}

.hero-subtitle {
  font-size: var(--font-size-lg);
  color: var(--color-text-secondary);
  max-width: 560px;
  margin: 0 auto;
  line-height: 1.6;
}

/* --- Tool Cards --- */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-5);
  margin-bottom: var(--space-16);
}

.tool-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-8);
  text-align: center;
  transition: all var(--transition-base);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-4);
}

.tool-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-accent);
  color: var(--color-text);
}

.tool-card-icon {
  width: 64px;
  height: 64px;
  min-width: 64px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

/* Tool card icon colors */
.icon-blue    { background: rgba(59,130,246,0.1);  color: #3b82f6; }
.icon-violet  { background: rgba(139,92,246,0.1);  color: #8b5cf6; }
.icon-emerald { background: rgba(16,185,129,0.1);  color: #10b981; }
.icon-rose    { background: rgba(244,63,94,0.1);   color: #f43f5e; }
.icon-amber   { background: rgba(245,158,11,0.1);  color: #f59e0b; }
.icon-cyan    { background: rgba(6,182,212,0.1);   color: #06b6d4; }

[data-theme="dark"] .icon-blue    { background: rgba(59,130,246,0.15); }
[data-theme="dark"] .icon-violet  { background: rgba(139,92,246,0.15); }
[data-theme="dark"] .icon-emerald { background: rgba(16,185,129,0.15); }
[data-theme="dark"] .icon-rose    { background: rgba(244,63,94,0.15); }
[data-theme="dark"] .icon-amber   { background: rgba(245,158,11,0.15); }
[data-theme="dark"] .icon-cyan    { background: rgba(6,182,212,0.15); }

.tool-card-icon svg {
  width: 32px;
  height: 32px;
}

.tool-card-title {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-text);
}

.tool-card-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* --- Feature section --- */
.features {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-8);
  padding: var(--space-12) 0;
  border-top: 1px solid var(--color-border);
}

.feature {
  text-align: center;
}

.feature-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto var(--space-4);
}

.feature-icon svg {
  width: 24px;
  height: 24px;
}

.feature-title {
  font-size: var(--font-size-base);
  font-weight: 600;
  margin-bottom: var(--space-2);
}

.feature-desc {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: 1.5;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-sm);
  font-weight: 500;
  font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-accent);
  color: var(--color-text-inverse);
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  color: var(--color-text-inverse);
}

.btn-secondary {
  background: var(--color-surface);
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover {
  background: var(--color-surface-hover);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.btn-ghost {
  color: var(--color-text-secondary);
}

.btn-ghost:hover {
  color: var(--color-text);
  background: var(--color-accent-subtle);
}

.btn-danger {
  color: var(--color-error);
}

.btn-danger:hover {
  background: var(--color-error-bg);
}

.btn svg {
  width: 18px;
  height: 18px;
}

.btn-lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--font-size-base);
  border-radius: var(--radius-md);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* --- Dropzone --- */
.dropzone {
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-12) var(--space-8);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-base);
  background: var(--color-surface);
}

.dropzone:hover {
  border-color: var(--color-accent);
  background: var(--color-accent-subtle);
}

.dropzone.drag-over {
  border-color: var(--color-accent);
  background: var(--color-accent-light);
  transform: scale(1.01);
}

.dropzone-icon {
  width: 56px;
  height: 56px;
  margin: 0 auto var(--space-4);
  color: var(--color-text-tertiary);
}

.dropzone-icon svg {
  width: 100%;
  height: 100%;
}

.dropzone-text {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-2);
}

.dropzone-text strong {
  color: var(--color-accent);
}

.dropzone-hint {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
}

/* --- Controls Panel --- */
.controls-panel {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  margin-bottom: var(--space-6);
}

.controls-row {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  flex-wrap: wrap;
}

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

.control-label {
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
}

.control-value {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-accent);
  min-width: 40px;
  text-align: right;
}

/* Range slider */
input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 200px;
  height: 6px;
  border-radius: var(--radius-full);
  background: var(--color-border);
  outline: none;
  transition: background var(--transition-fast);
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--color-accent);
  cursor: pointer;
  border: 3px solid var(--color-surface);
  box-shadow: var(--shadow-sm);
}

input[type="range"]::-moz-range-thumb {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--color-accent);
  cursor: pointer;
  border: 3px solid var(--color-surface);
  box-shadow: var(--shadow-sm);
}

/* Number input */
input[type="number"] {
  width: 100px;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-text);
  text-align: center;
  transition: border-color var(--transition-fast);
}

input[type="number"]:focus {
  outline: none;
  border-color: var(--color-accent);
}

/* Color input */
input[type="color"] {
  width: 40px;
  height: 40px;
  padding: 2px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  cursor: pointer;
}

/* Select */
select {
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  background: var(--color-surface);
  color: var(--color-text);
  cursor: pointer;
  transition: border-color var(--transition-fast);
}

select:focus {
  outline: none;
  border-color: var(--color-accent);
}

/* Toggle switch */
.toggle {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  cursor: pointer;
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.toggle-track {
  width: 40px;
  height: 22px;
  border-radius: var(--radius-full);
  background: var(--color-border);
  position: relative;
  transition: background var(--transition-fast);
}

.toggle-track::after {
  content: '';
  position: absolute;
  top: 3px;
  left: 3px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: white;
  transition: transform var(--transition-fast);
  box-shadow: var(--shadow-sm);
}

.toggle input {
  display: none;
}

.toggle input:checked + .toggle-track {
  background: var(--color-accent);
}

.toggle input:checked + .toggle-track::after {
  transform: translateX(18px);
}

/* --- Tabs --- */
.tabs {
  display: flex;
  gap: var(--space-1);
  margin-bottom: var(--space-6);
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 0;
}

.tab {
  padding: var(--space-3) var(--space-4);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  transition: all var(--transition-fast);
}

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

.tab.active {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* --- Preset buttons --- */
.preset-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: var(--space-3);
}

.preset-btn {
  padding: var(--space-3) var(--space-4);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  text-align: left;
  transition: all var(--transition-fast);
}

.preset-btn:hover {
  border-color: var(--color-accent);
  background: var(--color-accent-subtle);
}

.preset-btn.active {
  border-color: var(--color-accent);
  background: var(--color-accent-light);
}

.preset-name {
  font-size: var(--font-size-sm);
  font-weight: 500;
  display: block;
}

.preset-size {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
}

/* --- Results --- */
.results-section {
  margin-top: var(--space-6);
}

.results-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-4);
  flex-wrap: wrap;
  gap: var(--space-3);
}

.results-count {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.results-actions {
  display: flex;
  gap: var(--space-2);
}

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

.result-item {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-4);
  transition: border-color var(--transition-fast);
}

.result-item:hover {
  border-color: var(--color-border);
}

.result-thumb {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-sm);
  object-fit: cover;
  background: var(--color-bg);
  flex-shrink: 0;
}

.result-info {
  flex: 1;
  min-width: 0;
}

.result-name {
  font-size: var(--font-size-sm);
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  margin-bottom: var(--space-1);
}

.result-meta {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
  flex-wrap: wrap;
}

.result-size {
  color: var(--color-text-secondary);
}

.result-arrow {
  color: var(--color-text-tertiary);
}

.result-reduction {
  color: var(--color-success);
  font-weight: 600;
}

.result-increase {
  color: var(--color-error);
  font-weight: 600;
}

.result-dimensions {
  color: var(--color-text-tertiary);
}

.result-actions {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}
.result-remove-btn {
  background: none;
  border: none;
  padding: 4px;
  cursor: pointer;
  color: var(--color-text-tertiary);
  opacity: 0.5;
  transition: opacity var(--transition-fast), color var(--transition-fast);
}
.result-remove-btn:hover {
  opacity: 1;
  color: var(--color-danger, #ef4444);
  background: none;
}

/* --- Alert / Banner --- */
.alert {
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-sm);
  font-size: var(--font-size-sm);
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
}

.alert-warning {
  background: var(--color-warning-bg);
  color: var(--color-warning);
  border: 1px solid rgba(249, 171, 0, 0.15);
}

.alert-error {
  background: var(--color-error-bg);
  color: var(--color-error);
  border: 1px solid rgba(234, 67, 53, 0.15);
}

.alert-info {
  background: var(--color-accent-light);
  color: var(--color-accent);
  border: 1px solid rgba(84, 122, 192, 0.15);
}

.alert svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
  margin-top: 1px;
}

/* --- Page header (tool pages) --- */
.page-header {
  text-align: center;
  margin-bottom: var(--space-8);
}

.page-title {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  margin-bottom: var(--space-2);
  letter-spacing: -0.01em;
}

.page-desc {
  font-size: var(--font-size-base);
  color: var(--color-text-secondary);
}

/* --- Progress --- */
.progress-bar {
  width: 100%;
  height: 4px;
  background: var(--color-border);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--color-accent);
  border-radius: var(--radius-full);
  transition: width var(--transition-base);
}

/* --- Spinner --- */
.spinner {
  width: 20px;
  height: 20px;
  border: 2px solid var(--color-border);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* --- FAQ --- */
.faq-section {
  margin-bottom: var(--space-16);
}

.faq-section h2 {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--space-6);
}

.faq-list {
  max-width: var(--content-width);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.faq-list details {
  border-bottom: 1px solid var(--color-border);
}

.faq-list summary {
  padding: var(--space-4) 0;
  font-size: var(--font-size-base);
  font-weight: 600;
  color: var(--color-text);
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.faq-list summary::-webkit-details-marker {
  display: none;
}

.faq-list summary::after {
  content: '+';
  font-size: 1.3rem;
  font-weight: 400;
  color: var(--color-text-secondary);
}

.faq-list details[open] summary::after {
  content: '−';
}

.faq-list details p {
  padding: var(--space-3) 0 var(--space-4);
  border-top: 1px solid var(--color-border);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin: 0;
  animation: faqFadeIn 0.3s ease;
}

@keyframes faqFadeIn {
  from {
    opacity: 0;
    transform: translateY(-8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* --- Footer --- */
.footer {
  border-top: 1px solid var(--color-border);
  padding: var(--space-8) var(--space-6);
  margin-top: auto;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-4);
}

.footer-links {
  display: flex;
  gap: var(--space-4);
}

.footer-link {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
}

.footer-link:hover {
  color: var(--color-text-secondary);
}

.footer-copy {
  font-size: var(--font-size-sm);
  color: var(--color-text-tertiary);
}

/* --- Guide/Article content --- */
.article-content {
  line-height: 1.8;
}

.article-content h2 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  margin: var(--space-10) 0 var(--space-4);
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border);
}

.article-content h2:first-child {
  border-top: none;
  margin-top: 0;
  padding-top: 0;
}

.article-content h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin: var(--space-8) 0 var(--space-3);
}

.article-content p {
  margin-bottom: var(--space-4);
  color: var(--color-text-secondary);
}

.article-content ul, .article-content ol {
  margin-bottom: var(--space-4);
  padding-left: var(--space-6);
  color: var(--color-text-secondary);
}

.article-content li {
  margin-bottom: var(--space-2);
}

.article-content table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: var(--space-6);
  font-size: var(--font-size-sm);
}

.article-content th,
.article-content td {
  padding: var(--space-3) var(--space-4);
  text-align: left;
  border-bottom: 1px solid var(--color-border);
}

.article-content th {
  font-weight: 600;
  background: var(--color-accent-subtle);
}

.article-content strong {
  font-weight: 600;
  color: var(--color-text);
}

/* --- Back to Top --- */
.back-to-top {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  color: var(--color-text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.25s, visibility 0.25s, transform 0.25s, background 0.15s, color 0.15s;
  z-index: 90;
  box-shadow: var(--shadow);
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: #fff;
}

.back-to-top svg {
  width: 20px;
  height: 20px;
}

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

.text-center { text-align: center; }
.text-secondary { color: var(--color-text-secondary); }
.mt-4 { margin-top: var(--space-4); }
.mt-8 { margin-top: var(--space-8); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }

/* --- Responsive --- */

/* Tablet (640px+) */
@media (max-width: 1024px) {
  .tool-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-4);
  }

  .features {
    gap: var(--space-6);
  }
}

@media (max-width: 768px) {
  :root {
    --font-size-3xl: 1.75rem;
    --font-size-4xl: 2rem;
  }

  .nav {
    display: none;
  }

  .menu-btn {
    display: flex;
  }

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

  .tool-card {
    padding: var(--space-6);
    flex-direction: row;
    text-align: left;
  }

  .tool-card-icon {
    width: 52px;
    height: 52px;
    min-width: 52px;
    min-height: 52px;
  }

  .features {
    grid-template-columns: 1fr;
    gap: var(--space-6);
  }

  .hero {
    padding: var(--space-10) 0 var(--space-8);
  }

  .controls-row {
    flex-direction: column;
    align-items: stretch;
  }

  input[type="range"] {
    width: 100%;
  }

  .result-item {
    flex-wrap: wrap;
  }

  .result-actions {
    width: 100%;
    margin-top: var(--space-2);
  }

  .result-actions .btn {
    width: 100%;
  }

  .footer-inner {
    flex-direction: column;
    text-align: center;
  }

  .preset-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  .main {
    padding: var(--space-6) var(--space-4);
  }

  .header-inner {
    padding: 0 var(--space-4);
  }

  .dropzone {
    padding: var(--space-8) var(--space-4);
  }

  .preset-grid {
    grid-template-columns: 1fr;
  }
}

/* --- Lightbox (Image Zoom) --- */
.lightbox-overlay {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: rgba(0, 0, 0, 0.92);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.2s ease;
  cursor: zoom-out;
}

.lightbox-overlay.active {
  opacity: 1;
}

.lightbox-img {
  max-width: 90vw;
  max-height: 85vh;
  border-radius: var(--radius);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
  transform: scale(0.92);
  transition: transform 0.25s ease;
  object-fit: contain;
}

.lightbox-overlay.active .lightbox-img {
  transform: scale(1);
}

.lightbox-close {
  position: absolute;
  top: 16px;
  right: 20px;
  width: 40px;
  height: 40px;
  border: none;
  background: rgba(255, 255, 255, 0.15);
  color: #fff;
  border-radius: 50%;
  font-size: 1.25rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s;
}

.lightbox-close:hover {
  background: rgba(255, 255, 255, 0.3);
}

.lightbox-label {
  position: absolute;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);
  color: rgba(255, 255, 255, 0.8);
  font-size: 0.85rem;
  background: rgba(0, 0, 0, 0.5);
  padding: 6px 16px;
  border-radius: 20px;
  white-space: nowrap;
}

.zoomable {
  cursor: zoom-in;
  transition: opacity 0.15s;
}

.zoomable:hover {
  opacity: 0.85;
}

/* --- File Strip (thumbnail strip for multi-image) --- */
.controls-tip {
  font-size: var(--font-size-xs);
  color: var(--color-text-tertiary);
  text-align: center;
  padding: var(--space-1) 0;
}

.file-strip {
  display: flex;
  gap: var(--space-2);
  padding: var(--space-3);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-4);
  overflow-x: auto;
  align-items: center;
}
.file-thumb {
  position: relative;
  width: 56px;
  height: 56px;
  border-radius: var(--radius-sm);
  border: 2px solid transparent;
  cursor: pointer;
  flex-shrink: 0;
  overflow: hidden;
  transition: border-color var(--transition-fast);
}
.file-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.file-thumb:hover { border-color: var(--color-text-tertiary); }
.file-thumb.active { border-color: var(--color-accent); }
.file-thumb-remove {
  position: absolute;
  top: -2px;
  right: -2px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--color-danger, #ef4444);
  color: #fff;
  border: none;
  font-size: 11px;
  line-height: 18px;
  text-align: center;
  cursor: pointer;
  opacity: 0;
  transition: opacity var(--transition-fast);
  padding: 0;
}
.file-thumb:hover .file-thumb-remove { opacity: 1; }
.file-add-btn {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-sm);
  border: 2px dashed var(--color-border);
  background: transparent;
  cursor: pointer;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-tertiary);
  font-size: 1.5rem;
  transition: border-color var(--transition-fast), color var(--transition-fast);
}
.file-add-btn:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

@media (max-width: 480px) {
  .file-thumb, .file-add-btn {
    width: 48px;
    height: 48px;
  }
}