/* ===================================================================
   ToolNest Design System & Stylesheet
   Modern, responsive, dark-mode ready, zero-framework vanilla CSS.
   Tested for 360px mobile viewports up to 4K desktops.
   =================================================================== */

/* Google Fonts: Inter */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500&display=swap');

:root {
  /* Color Palette - Light Theme */
  --bg-primary: #f8fafc;
  --bg-surface: #ffffff;
  --bg-elevated: #ffffff;
  --bg-subtle: #f1f5f9;
  --border-subtle: #e2e8f0;
  --border-strong: #cbd5e1;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --text-inverse: #ffffff;

  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-light: #eff6ff;
  --primary-border: #bfdbfe;

  --accent: #0ea5e9;
  --accent-light: #e0f2fe;

  --success: #10b981;
  --success-bg: #ecfdf5;
  --warning: #f59e0b;
  --warning-bg: #fffbeb;
  --danger: #ef4444;
  --danger-bg: #fef2f2;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --max-width: 1200px;
  --header-height: 64px;
}

[data-theme="dark"] {
  /* Color Palette - Dark Theme */
  --bg-primary: #0b1329;
  --bg-surface: #111e38;
  --bg-elevated: #182848;
  --bg-subtle: #1e3156;
  --border-subtle: #243b66;
  --border-strong: #334e80;

  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-inverse: #0f172a;

  --primary: #3b82f6;
  --primary-hover: #60a5fa;
  --primary-light: #172554;
  --primary-border: #1e40af;

  --accent: #38bdf8;
  --accent-light: #082f49;

  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

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

a {
  color: var(--primary);
  text-decoration: none;
  transition: color 0.15s ease;
}

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

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

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

/* Accessible focus ring */
*:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* Layout Container */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: 1.25rem;
  padding-right: 1.25rem;
}

/* Header & Navigation */
.site-header {
  height: var(--header-height);
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(8px);
}

.header-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 800;
  font-size: 1.25rem;
  color: var(--text-primary);
  text-decoration: none;
}

.brand-icon {
  width: 28px;
  height: 28px;
  color: var(--primary);
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.nav-link {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.9375rem;
}

.nav-link:hover, .nav-link.active {
  color: var(--primary);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle-btn {
  background: transparent;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: 0.5rem;
  color: var(--text-secondary);
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s ease;
}

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

/* Server pre-warm alert banner */
.api-alert-banner {
  background-color: var(--primary-light);
  border-bottom: 1px solid var(--primary-border);
  color: var(--primary);
  padding: 0.625rem 1rem;
  font-size: 0.875rem;
  display: none;
  text-align: center;
  animation: fadeIn 0.2s ease-in;
}

.api-alert-banner.active {
  display: block;
}

/* Main Content Wrapper */
.main-content {
  flex: 1;
  padding-top: 2rem;
  padding-bottom: 3rem;
}

/* Hero Section */
.hero-section {
  text-align: center;
  padding: 3rem 0 2rem;
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
}

.hero-title-highlight {
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto 1.5rem;
}

.hero-badges {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.75rem;
  margin-bottom: 2rem;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.375rem;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-full);
  font-size: 0.8125rem;
  font-weight: 600;
  background-color: var(--bg-subtle);
  color: var(--text-secondary);
  border: 1px solid var(--border-subtle);
}

/* Tool Grid & Cards */
.category-block {
  margin-bottom: 3rem;
}

.category-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
}

.tool-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
  box-shadow: var(--shadow-sm);
  text-decoration: none;
}

.tool-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--primary-border);
}

.tool-card-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}

.tool-icon-wrapper {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background-color: var(--primary-light);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.tool-card-title {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--text-primary);
}

.tool-card-desc {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  margin-bottom: 1rem;
  flex: 1;
}

.tool-card-footer {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--primary);
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

/* Tool Page Specific Layout */
.tool-page-header {
  text-align: center;
  max-width: 768px;
  margin: 0 auto 2rem;
}

.tool-page-h1 {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 800;
  margin-bottom: 0.75rem;
  letter-spacing: -0.01em;
}

.tool-page-intro {
  font-size: 1.0625rem;
  color: var(--text-secondary);
}

/* Tool Workspace Interface Card */
.tool-workspace {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 2rem;
  box-shadow: var(--shadow-md);
  margin-bottom: 2.5rem;
}

@media (max-width: 640px) {
  .tool-workspace {
    padding: 1.25rem;
  }
}

/* Drag-and-drop Upload Area */
.dropzone-container {
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius-md);
  padding: 3rem 1.5rem;
  text-align: center;
  background-color: var(--bg-subtle);
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
}

.dropzone-container:hover, .dropzone-container.dragover {
  border-color: var(--primary);
  background-color: var(--primary-light);
}

.dropzone-icon {
  width: 48px;
  height: 48px;
  margin: 0 auto 1rem;
  color: var(--primary);
}

.dropzone-title {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.dropzone-subtitle {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.file-input-hidden {
  display: none;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.9375rem;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all 0.15s ease;
  text-decoration: none;
}

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

.btn-primary:hover:not(:disabled) {
  background-color: var(--primary-hover);
  color: var(--text-inverse);
}

.btn-primary:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.btn-secondary {
  background-color: var(--bg-subtle);
  color: var(--text-primary);
  border-color: var(--border-subtle);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--border-subtle);
}

.btn-block {
  width: 100%;
}

/* Privacy Guarantee Tagline */
.privacy-notice {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.375rem;
  font-size: 0.8125rem;
  color: var(--text-muted);
  margin-top: 1rem;
  text-align: center;
}

.privacy-notice-icon {
  width: 14px;
  height: 14px;
  color: var(--success);
}

/* Progress Bar */
.progress-container {
  display: none;
  margin-top: 1.5rem;
}

.progress-container.active {
  display: block;
}

.progress-bar-bg {
  background-color: var(--bg-subtle);
  border-radius: var(--radius-full);
  height: 8px;
  overflow: hidden;
}

.progress-bar-fill {
  background-color: var(--primary);
  height: 100%;
  width: 0%;
  transition: width 0.2s ease;
}

.progress-text {
  font-size: 0.8125rem;
  color: var(--text-secondary);
  display: flex;
  justify-content: space-between;
  margin-top: 0.5rem;
}

/* Content Explanations & How-To */
.content-section {
  max-width: 800px;
  margin: 0 auto 3rem;
}

.section-h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.how-to-steps {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  margin-bottom: 2rem;
}

.step-card {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  padding: 1rem;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
}

.step-number {
  background-color: var(--primary-light);
  color: var(--primary);
  font-weight: 700;
  font-size: 0.875rem;
  width: 28px;
  height: 28px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.article-prose {
  font-size: 1.0625rem;
  line-height: 1.75;
  color: var(--text-secondary);
}

.article-prose p {
  margin-bottom: 1.25rem;
}

.article-prose h3 {
  color: var(--text-primary);
  font-size: 1.25rem;
  font-weight: 700;
  margin: 1.5rem 0 0.5rem;
}

/* FAQ Accordion */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

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

.faq-question {
  width: 100%;
  padding: 1.25rem;
  text-align: left;
  background: transparent;
  border: none;
  font-weight: 600;
  font-size: 1rem;
  color: var(--text-primary);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}

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

.faq-answer {
  display: none;
  padding: 0 1.25rem 1.25rem;
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

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

.faq-icon {
  width: 20px;
  height: 20px;
  transition: transform 0.2s ease;
  flex-shrink: 0;
}

.faq-item.open .faq-icon {
  transform: rotate(180deg);
}

/* Reserved Ad Slot Container (CLS Guard) */
.ad-slot-container {
  display: none; /* Stays hidden until explicitly enabled */
  margin: 1.5rem 0;
  text-align: center;
  background-color: var(--bg-subtle);
  border: 1px dashed var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.ad-slot-container.enabled {
  display: flex;
  align-items: center;
  justify-content: center;
}

.ad-slot-banner {
  min-height: 90px;
  max-width: 728px;
  margin-left: auto;
  margin-right: auto;
}

/* Footer */
.site-footer {
  background-color: var(--bg-surface);
  border-top: 1px solid var(--border-subtle);
  padding: 3rem 0 2rem;
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
  margin-bottom: 2rem;
}

.footer-col-title {
  font-size: 0.875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.625rem;
}

.footer-link {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

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

.footer-bottom {
  border-top: 1px solid var(--border-subtle);
  padding-top: 1.5rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  font-size: 0.8125rem;
  color: var(--text-muted);
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: translateY(0); }
}