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

:root {
  --primary: #6366f1;
  --primary-dark: #4f46e5;
  --primary-light: #e0e7ff;
  --accent: #10b981;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-400: #9ca3af;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-900: #111827;
  --white: #ffffff;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 10px 10px -5px rgba(0,0,0,0.04);
  --radius: 12px;
  --radius-lg: 20px;
  --transition: 0.2s ease;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial,
    "Noto Sans", "Noto Sans CJK SC", "PingFang SC", "Hiragino Sans GB",
    "Microsoft YaHei", sans-serif;
  color: var(--gray-700);
  background: var(--gray-50);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Navigation ===== */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--gray-200);
  padding: 0 24px;
}

.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.nav-logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  letter-spacing: -0.5px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 24px;
  list-style: none;
}

.nav-links a {
  color: var(--gray-600);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color var(--transition);
}

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

/* Language Switcher */
.lang-switcher {
  position: relative;
}

.lang-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border: 1px solid var(--gray-200);
  border-radius: 8px;
  background: var(--white);
  cursor: pointer;
  font-size: 0.875rem;
  color: var(--gray-700);
  transition: all var(--transition);
  white-space: nowrap;
}

.lang-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.lang-btn svg { flex-shrink: 0; }

.lang-dropdown {
  position: absolute;
  right: 0;
  top: calc(100% + 8px);
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  min-width: 160px;
  overflow: hidden;
  display: none;
  z-index: 200;
}

.lang-dropdown.open { display: block; }

.lang-option {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 16px;
  cursor: pointer;
  font-size: 0.875rem;
  color: var(--gray-700);
  transition: background var(--transition);
}

.lang-option:hover { background: var(--gray-50); }
.lang-option.active { background: var(--primary-light); color: var(--primary-dark); font-weight: 500; }
.lang-flag { font-size: 1.1em; }

/* ===== Hero ===== */
.hero {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: var(--white);
  text-align: center;
  padding: 72px 24px 80px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.05'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(255,255,255,0.2);
  border: 1px solid rgba(255,255,255,0.3);
  border-radius: 100px;
  padding: 6px 16px;
  font-size: 0.85rem;
  margin-bottom: 24px;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -1px;
  margin-bottom: 8px;
}

.hero-subtitle {
  font-size: clamp(1.5rem, 3vw, 2.5rem);
  font-weight: 700;
  opacity: 0.9;
  margin-bottom: 16px;
}

.hero-desc {
  font-size: 1.1rem;
  opacity: 0.85;
  max-width: 540px;
  margin: 0 auto;
}

/* ===== Upload Section ===== */
.upload-section {
  max-width: 800px;
  margin: -40px auto 0;
  padding: 0 24px 64px;
  position: relative;
  z-index: 10;
}

.upload-card {
  background: var(--white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  padding: 40px;
}

.upload-area {
  border: 2.5px dashed var(--gray-200);
  border-radius: var(--radius);
  padding: 60px 24px;
  text-align: center;
  cursor: pointer;
  transition: all var(--transition);
  position: relative;
}

.upload-area:hover,
.upload-area.drag-over {
  border-color: var(--primary);
  background: var(--primary-light);
}

.upload-area input[type="file"] {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
  width: 100%;
  height: 100%;
}

.upload-icon {
  width: 64px;
  height: 64px;
  background: var(--primary-light);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 16px;
}

.upload-icon svg { color: var(--primary); }

.upload-drag-text {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--gray-700);
  margin-bottom: 8px;
}

.upload-or {
  color: var(--gray-400);
  font-size: 0.875rem;
  margin-bottom: 16px;
}

.upload-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--primary);
  color: var(--white);
  border: none;
  border-radius: 10px;
  padding: 12px 28px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition), transform var(--transition);
  pointer-events: none; /* let file input handle click */
}

.upload-area:hover .upload-btn { background: var(--primary-dark); }

.upload-formats {
  margin-top: 16px;
  font-size: 0.8rem;
  color: var(--gray-400);
}

/* ===== Processing State ===== */
.processing {
  text-align: center;
  padding: 40px;
  display: none;
}

.spinner {
  width: 52px;
  height: 52px;
  border: 4px solid var(--primary-light);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin: 0 auto 16px;
}

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

.processing-text {
  font-size: 1rem;
  color: var(--gray-600);
}

/* ===== Result Section ===== */
.result-section {
  display: none;
  margin-top: 32px;
}

.result-title {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--accent);
  text-align: center;
  margin-bottom: 24px;
}

.result-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 24px;
}

.result-item {
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--gray-200);
}

.result-label {
  padding: 8px 16px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--gray-600);
  background: var(--gray-50);
  border-bottom: 1px solid var(--gray-200);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.result-img {
  width: 100%;
  height: 260px;
  object-fit: contain;
  background: repeating-conic-gradient(var(--gray-200) 0% 25%, var(--white) 0% 50%) 0 0 / 20px 20px;
}

.result-img.original-img { background: var(--gray-100); }

.result-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn-download {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--accent);
  color: var(--white);
  border: none;
  border-radius: 10px;
  padding: 14px 32px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: filter var(--transition);
}

.btn-download:hover { filter: brightness(1.08); }

.btn-try-another {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: transparent;
  color: var(--gray-600);
  border: 1.5px solid var(--gray-200);
  border-radius: 10px;
  padding: 14px 24px;
  font-size: 1rem;
  cursor: pointer;
  transition: all var(--transition);
}

.btn-try-another:hover {
  border-color: var(--primary);
  color: var(--primary);
}

/* ===== Error Toast ===== */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(100px);
  background: #ef4444;
  color: var(--white);
  padding: 14px 24px;
  border-radius: 12px;
  box-shadow: var(--shadow-lg);
  font-size: 0.9rem;
  font-weight: 500;
  z-index: 999;
  transition: transform 0.3s ease;
  max-width: 90vw;
  text-align: center;
}

.toast.show { transform: translateX(-50%) translateY(0); }

/* ===== Privacy Banner ===== */
.privacy-banner {
  background: #ecfdf5;
  border: 1px solid #a7f3d0;
  border-radius: var(--radius);
  padding: 12px 20px;
  text-align: center;
  font-size: 0.875rem;
  color: #065f46;
  margin-top: 24px;
}

/* ===== Features Section ===== */
.features {
  background: var(--white);
  padding: 80px 24px;
}

.section-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.section-title {
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 700;
  color: var(--gray-900);
  text-align: center;
  margin-bottom: 48px;
  letter-spacing: -0.5px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 24px;
}

.feature-card {
  background: var(--gray-50);
  border-radius: var(--radius);
  padding: 28px 24px;
  transition: box-shadow var(--transition), transform var(--transition);
}

.feature-card:hover {
  box-shadow: var(--shadow);
  transform: translateY(-2px);
}

.feature-icon {
  font-size: 2rem;
  margin-bottom: 12px;
}

.feature-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-bottom: 8px;
}

.feature-desc {
  font-size: 0.875rem;
  color: var(--gray-600);
  line-height: 1.6;
}

/* ===== FAQ Section ===== */
.faq {
  padding: 80px 24px;
  background: var(--gray-50);
}

.faq-list {
  max-width: 720px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.faq-item {
  background: var(--white);
  border-radius: var(--radius);
  border: 1px solid var(--gray-200);
  overflow: hidden;
}

.faq-question {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 24px;
  background: none;
  border: none;
  text-align: left;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--gray-800, #1f2937);
  cursor: pointer;
  gap: 16px;
  transition: color var(--transition);
}

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

.faq-chevron {
  flex-shrink: 0;
  transition: transform 0.25s ease;
  color: var(--gray-400);
}

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

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, padding 0.3s ease;
  font-size: 0.9rem;
  color: var(--gray-600);
  line-height: 1.7;
  padding: 0 24px;
}

.faq-item.open .faq-answer {
  max-height: 200px;
  padding: 0 24px 20px;
}

/* ===== Footer ===== */
.footer {
  background: var(--gray-900);
  color: var(--gray-400);
  padding: 40px 24px;
  text-align: center;
  font-size: 0.875rem;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.footer-links a {
  color: var(--gray-400);
  text-decoration: none;
  transition: color var(--transition);
}

.footer-links a:hover { color: var(--white); }

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .nav-links { display: none; }
  .upload-card { padding: 24px 16px; }
  .upload-area { padding: 40px 16px; }
  .result-grid { grid-template-columns: 1fr; }
  .result-img { height: 200px; }
  .hero { padding: 56px 20px 72px; }
}