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

:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #dbeafe;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --text: #1e293b;
  --text-light: #64748b;
  --border: #e2e8f0;
  --success: #16a34a;
  --error: #dc2626;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-lg: 0 10px 25px rgba(0,0,0,0.08), 0 4px 10px rgba(0,0,0,0.04);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "Noto Sans", "Noto Sans CJK SC",
    "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ===== Header ===== */
.site-header {
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 100;
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 8px;
}

.logo-icon {
  font-size: 1.5rem;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  width: 24px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: 0.3s;
}

.main-nav ul {
  display: flex;
  gap: 4px;
  list-style: none;
}

.main-nav a {
  padding: 8px 14px;
  border-radius: 8px;
  text-decoration: none;
  color: var(--text-light);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 0.2s;
}

.main-nav a:hover,
.main-nav a.active {
  background: var(--primary-light);
  color: var(--primary-dark);
}

/* ===== Layout ===== */
.container {
  width: 100%;
  max-width: 900px;
  margin: 0 auto;
  padding: 0 20px;
}

main {
  flex: 1;
  padding: 32px 0 64px;
}

/* ===== Hero / Page Title ===== */
.page-title {
  text-align: center;
  margin-bottom: 12px;
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.02em;
}

.page-subtitle {
  text-align: center;
  color: var(--text-light);
  font-size: 1.05rem;
  margin-bottom: 40px;
}

/* ===== Tool Grid (Homepage) ===== */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 20px;
}

.tool-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 24px;
  text-decoration: none;
  color: inherit;
  transition: all 0.25s;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

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

.tool-card .icon {
  font-size: 2rem;
  margin-bottom: 4px;
}

.tool-card h3 {
  font-size: 1.1rem;
  font-weight: 600;
}

.tool-card p {
  font-size: 0.875rem;
  color: var(--text-light);
}

/* ===== Tool Page Layout ===== */
.tool-wrapper {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px;
  box-shadow: var(--shadow);
}

.tool-wrapper h1 {
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.tool-wrapper > .desc {
  color: var(--text-light);
  margin-bottom: 28px;
  font-size: 0.95rem;
}

/* ===== Form Controls ===== */
.field {
  margin-bottom: 20px;
}

.field label {
  display: block;
  font-weight: 500;
  margin-bottom: 6px;
  font-size: 0.9rem;
}

.input,
textarea.input,
select.input {
  width: 100%;
  padding: 12px 16px;
  border: 2px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  font-family: inherit;
  background: var(--bg);
  color: var(--text);
  transition: border-color 0.2s;
}

.input:focus,
textarea.input:focus,
select.input:focus {
  outline: none;
  border-color: var(--primary);
}

textarea.input {
  min-height: 160px;
  resize: vertical;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

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

.btn-secondary {
  background: var(--primary-light);
  color: var(--primary-dark);
}

.btn-secondary:hover {
  background: #bfdbfe;
}

.btn-row {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

/* ===== Result Display ===== */
.result-box {
  background: var(--bg);
  border: 2px solid var(--border);
  border-radius: 8px;
  padding: 20px 24px;
  margin-top: 8px;
  min-height: 56px;
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 1.05rem;
  word-break: break-all;
}

.result-box .label {
  color: var(--text-light);
  font-size: 0.85rem;
  font-weight: 500;
}

.result-box .value {
  font-weight: 700;
  color: var(--primary-dark);
}

.result-box .copy-btn {
  margin-left: auto;
  font-size: 0.8rem;
  padding: 6px 14px;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 6px;
  cursor: pointer;
  color: var(--text-light);
  transition: all 0.2s;
}

.result-box .copy-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.result-box .copy-btn.copied {
  background: var(--success);
  color: #fff;
  border-color: var(--success);
}

/* ===== Stats Grid (Word Counter etc.) ===== */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  gap: 16px;
  margin-top: 24px;
}

.stat-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 20px;
  text-align: center;
}

.stat-card .num {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--primary);
}

.stat-card .name {
  font-size: 0.8rem;
  color: var(--text-light);
  margin-top: 4px;
}

/* ===== Color Converter Specific ===== */
.color-preview {
  width: 100%;
  height: 80px;
  border-radius: 8px;
  border: 2px solid var(--border);
  margin-bottom: 20px;
}

.color-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}

.color-row .format {
  width: 50px;
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--text-light);
}

.color-row .color-input {
  flex: 1;
}

/* ===== QR Generator Specific ===== */
.qr-preview {
  display: flex;
  justify-content: center;
  padding: 24px;
  background: #fff;
  border: 2px solid var(--border);
  border-radius: 8px;
  min-height: 260px;
  align-items: center;
}

.qr-preview img,
.qr-preview canvas {
  max-width: 240px;
}

.qr-preview .placeholder {
  color: var(--text-light);
  font-size: 0.9rem;
}

/* ===== Range Sliders ===== */
.range-group {
  display: flex;
  align-items: center;
  gap: 12px;
}

.range-group input[type="range"] {
  flex: 1;
  accent-color: var(--primary);
}

.range-group .range-val {
  width: 40px;
  text-align: center;
  font-weight: 600;
}

/* ===== Checkbox Grid ===== */
.checkbox-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 10px;
}

.checkbox-item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 14px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
  transition: all 0.2s;
}

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

.checkbox-item input {
  accent-color: var(--primary);
}

/* ===== Ad Placeholder ===== */
.ad-slot {
  width: 100%;
  min-height: 90px;
  margin: 32px 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #f1f5f9;
  border: 1px dashed #cbd5e1;
  border-radius: 8px;
  color: #94a3b8;
  font-size: 0.8rem;
}

/* ===== Content Section (SEO Text) ===== */
.content-section {
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border);
}

.content-section h2 {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 16px;
}

.content-section p {
  color: var(--text-light);
  margin-bottom: 12px;
  font-size: 0.95rem;
}

/* ===== Back Link ===== */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-light);
  text-decoration: none;
  font-size: 0.9rem;
  margin-bottom: 20px;
  transition: color 0.2s;
}

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

/* ===== Footer ===== */
.site-footer {
  background: var(--card-bg);
  border-top: 1px solid var(--border);
  padding: 24px 0;
  text-align: center;
  color: var(--text-light);
  font-size: 0.85rem;
}

.site-footer a {
  color: var(--text-light);
  text-decoration: none;
  margin: 0 8px;
}

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

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .page-title {
    font-size: 1.5rem;
  }
  .tool-wrapper {
    padding: 24px 20px;
  }
  .nav-toggle {
    display: flex;
  }
  .main-nav {
    display: none;
    position: absolute;
    top: 60px;
    left: 0;
    right: 0;
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
  }
  .main-nav.open {
    display: block;
  }
  .main-nav ul {
    flex-direction: column;
    padding: 8px 20px;
  }
}