/* ============================================
   251在线工具 · tool.251w.com
   内容区最大宽度 1600px
   ============================================ */
* { margin: 0; padding: 0; box-sizing: border-box; }

:root {
  --primary: #0d9488;
  --primary-deep: #0f766e;
  --accent: #0891b2;
  --dark: #0f172a;
  --text: #334155;
  --muted: #64748b;
  --bg: #f0fdfa;
  --panel: #ffffff;
  --border: #d5e5e2;
  --radius: 14px;
  --shadow: 0 8px 24px rgba(15, 23, 42, .06);
}

body {
  font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  min-height: 100vh;
}

.container { max-width: 1600px; margin: 0 auto; padding: 0 28px; }
a { text-decoration: none; color: inherit; }
button, input, textarea, select { font: inherit; }

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  min-height: 42px; padding: 0 20px; border-radius: 999px;
  border: none; cursor: pointer; font-weight: 600; transition: .2s;
}
.btn-sm { min-height: 36px; padding: 0 16px; font-size: 13px; }
.btn-primary { background: linear-gradient(90deg, var(--primary), var(--accent)); color: #fff; }
.btn-primary:hover { transform: translateY(-1px); filter: brightness(1.05); }
.btn-line { background: #fff; border: 1px solid var(--border); color: var(--dark); }
.btn-line:hover { border-color: var(--primary); color: var(--primary); }
.btn-ghost { border: 1px solid rgba(255,255,255,.35); color: #fff; background: transparent; }
.btn-ghost:hover { background: rgba(255,255,255,.12); }

/* header */
.header {
  background: linear-gradient(105deg, #042f2e 0%, #134e4a 55%, #0f766e 100%);
  color: #ccfbf1; position: sticky; top: 0; z-index: 50;
}
.header .container {
  display: flex; align-items: center; justify-content: space-between;
  gap: 20px; min-height: 72px;
}
.logo { display: flex; align-items: center; gap: 12px; color: #fff; }
.logo-mark {
  width: 42px; height: 42px; border-radius: 12px;
  background: linear-gradient(135deg, #2dd4bf, #22d3ee);
  color: #042f2e; font-weight: 800; font-size: 20px;
  display: flex; align-items: center; justify-content: center;
}
.logo-text b { display: block; font-size: 17px; line-height: 1.2; }
.logo-text small { font-size: 11px; opacity: .75; letter-spacing: .4px; }
.nav { display: flex; gap: 6px 18px; list-style: none; flex-wrap: wrap; }
.nav a { color: #99f6e4; font-size: 14px; font-weight: 500; }
.nav a:hover, .nav .active a { color: #fff; }
.h-actions { display: flex; align-items: center; gap: 10px; }
.burger {
  display: none; width: 42px; height: 42px; border: 0; border-radius: 10px;
  background: rgba(255,255,255,.1); flex-direction: column; justify-content: center; align-items: center; gap: 5px;
}
.burger span { width: 18px; height: 2px; background: #fff; display: block; }

/* home hero */
.home-hero {
  padding: 56px 0 40px;
  text-align: center;
  background:
    radial-gradient(circle at 12% 20%, rgba(45,212,191,.18), transparent 40%),
    radial-gradient(circle at 88% 10%, rgba(34,211,238,.16), transparent 36%),
    linear-gradient(180deg, #ecfeff 0%, var(--bg) 100%);
}
.home-hero h1 {
  font-size: clamp(30px, 3.4vw, 44px);
  color: var(--dark); line-height: 1.25; max-width: 900px;
  margin: 0 auto;
}
.home-hero .lead {
  margin: 14px auto 0; font-size: 16px; color: var(--muted); max-width: 780px;
}
.hero-meta {
  margin-top: 22px; display: flex; flex-wrap: wrap; gap: 10px;
  justify-content: center;
}
.hero-meta span {
  padding: 6px 14px; border-radius: 999px; background: #fff;
  border: 1px solid var(--border); font-size: 13px; color: var(--primary-deep); font-weight: 600;
}
.search-bar {
  margin: 28px auto 0; max-width: 640px; position: relative;
}
.search-bar input {
  width: 100%; height: 50px; border-radius: 14px; border: 1px solid var(--border);
  padding: 0 18px 0 46px; background: #fff; outline: none;
}
.search-bar input:focus { border-color: var(--primary); box-shadow: 0 0 0 3px rgba(13,148,136,.15); }
.search-bar svg {
  position: absolute; left: 16px; top: 50%; transform: translateY(-50%);
  width: 18px; height: 18px; color: var(--muted);
}

/* sections */
.section { padding: 28px 0 12px; }
.section-head {
  display: flex; align-items: end; justify-content: space-between;
  gap: 16px; margin-bottom: 18px;
}
.section-head h2 { font-size: 24px; color: var(--dark); }
.section-head p { color: var(--muted); font-size: 14px; }

.tool-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}
.tool-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 18px; box-shadow: var(--shadow); transition: .2s;
  display: flex; flex-direction: column; gap: 8px; min-height: 148px;
}
.tool-card:hover {
  transform: translateY(-3px); border-color: #99f6e4;
  box-shadow: 0 14px 28px rgba(13,148,136,.12);
}
.tc-cat { font-size: 12px; color: var(--primary); font-weight: 700; }
.tool-card b { font-size: 17px; color: var(--dark); line-height: 1.35; }
.tool-card p { font-size: 13px; color: var(--muted); line-height: 1.6; }

/* tool page */
.breadcrumb { padding: 16px 0 0; font-size: 13px; color: var(--muted); }
.breadcrumb .container { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
.breadcrumb a { color: var(--primary-deep); }
.tool-hero { padding: 28px 0 8px; }
.tool-cat { color: var(--primary); font-weight: 700; font-size: 13px; margin-bottom: 8px; }
.tool-hero h1 { font-size: clamp(26px, 3vw, 36px); color: var(--dark); }
.tool-lead { margin-top: 10px; color: var(--muted); max-width: 900px; }
.tool-workspace { padding: 18px 0 28px; }
.tool-panel {
  background: #fff; border: 1px solid var(--border); border-radius: 18px;
  padding: 28px; box-shadow: var(--shadow);
}
.form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px 18px; margin-bottom: 16px; }
.form-grid.two { grid-template-columns: 1fr 1fr; }
.form-grid.three { grid-template-columns: repeat(3, 1fr); }
label { display: flex; flex-direction: column; gap: 6px; font-size: 13px; color: var(--muted); font-weight: 600; }
label.block { display: flex; margin-top: 14px; }
label.check { flex-direction: row; align-items: center; gap: 8px; color: var(--text); }
input[type="text"], input[type="url"], input[type="number"], input[type="search"],
input[type="date"], input[type="datetime-local"], select, textarea {
  width: 100%; border: 1px solid var(--border); border-radius: 10px;
  padding: 10px 12px; background: #fff; color: var(--dark); outline: none;
}
textarea { resize: vertical; line-height: 1.55; }
input:focus, select:focus, textarea:focus {
  border-color: var(--primary); box-shadow: 0 0 0 3px rgba(13,148,136,.12);
}
.btn-row { display: flex; flex-wrap: wrap; gap: 10px; margin: 8px 0 4px; }
.btn-row.wrap { margin-bottom: 12px; }
.hint { font-size: 12px; color: var(--muted); font-weight: 500; margin: 4px 0 10px; }
.stat-row {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin: 16px 0;
}
.stat-item {
  background: #f0fdfa; border: 1px solid var(--border); border-radius: 12px; padding: 14px;
}
.stat-item span { display: block; font-size: 12px; color: var(--muted); }
.stat-item b { font-size: 22px; color: var(--dark); }
.table-wrap { overflow: auto; border: 1px solid var(--border); border-radius: 12px; margin-top: 12px; }
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { padding: 10px 12px; border-bottom: 1px solid var(--border); text-align: left; }
th { background: #f8fafc; color: var(--muted); font-size: 12px; }
.serp-box {
  background: #fff; border: 1px solid var(--border); border-radius: 12px;
  padding: 20px; min-height: 220px; box-shadow: inset 0 0 0 1px #f1f5f9;
}
.serp-url { color: #202124; font-size: 13px; margin-bottom: 4px; }
.serp-title { color: #1a0dab; font-size: 20px; line-height: 1.3; display: inline-block; margin-bottom: 6px; }
.serp-desc { color: #4d5156; font-size: 14px; line-height: 1.55; }
.heading-tree { margin-top: 14px; font-family: ui-monospace, Consolas, monospace; font-size: 13px; }
.heading-tree .h-row { padding: 6px 0; border-bottom: 1px dashed var(--border); }
.color-preview {
  min-height: 220px; border-radius: 16px; border: 1px solid var(--border);
}
.tool-seo { padding: 10px 0 48px; }
.seo-card {
  background: #fff; border: 1px solid var(--border); border-radius: 16px;
  padding: 28px; margin-bottom: 28px;
}
.seo-card h2 { font-size: 20px; color: var(--dark); margin-bottom: 10px; }
.seo-card h3 { font-size: 16px; color: var(--dark); margin: 18px 0 8px; }
.seo-card p, .seo-card li { color: var(--muted); font-size: 14px; }
.seo-card ul { padding-left: 18px; }
.related-tools h2 { font-size: 20px; color: var(--dark); margin-bottom: 14px; }
.tool-grid.related { grid-template-columns: repeat(3, 1fr); }

/* 404 */
.page-404 { padding: 72px 0; min-height: 50vh; }
.page-404-box {
  max-width: 680px; margin: 0 auto; text-align: center; background: #fff;
  border: 1px solid var(--border); border-radius: 18px; padding: 48px 28px;
}
.page-404-code {
  font-size: 84px; font-weight: 800; line-height: 1; color: var(--primary); margin-bottom: 10px;
}
.page-404-box h1 { font-size: 26px; color: var(--dark); margin-bottom: 10px; }
.page-404-box p { color: var(--muted); margin-bottom: 24px; }
.page-404-actions { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }


/* ---------- 友情链接 ---------- */
.friend-links {
  background: #fff;
  border-top: 1px solid var(--border);
  padding: 28px 0 8px;
  margin-top: 20px;
}
.friend-links-title {
  font-size: 15px; font-weight: 700; color: var(--dark); margin-bottom: 14px;
}
.friend-links-list {
  list-style: none; display: flex; flex-wrap: wrap; gap: 10px 18px;
}
.friend-links-list a { font-size: 13px; color: var(--muted); }
.friend-links-list a:hover { color: var(--primary); }

/* footer */
.footer {
  margin-top: 40px; background: #042f2e; color: #99f6e4; padding-top: 36px;
}
.footer-grid {
  display: grid; grid-template-columns: 1.4fr 1fr 1fr 1.2fr; gap: 24px; padding-bottom: 28px;
}
.f-brand b, .f-links h4, .f-note h4 { color: #ecfeff; display: block; margin-bottom: 12px; }
.f-brand p, .f-note p { font-size: 13px; line-height: 1.7; color: #5eead4; }
.f-links a { display: block; font-size: 14px; color: #99f6e4; margin: 8px 0; }
.f-links a:hover { color: #fff; }
.footer-copy {
  border-top: 1px solid rgba(153,246,228,.15); padding: 18px 0 28px; text-align: center;
  font-size: 13px; color: #5eead4;
}
.mobile-mask {
  display: none; position: fixed; inset: 0; background: rgba(15,23,42,.45); z-index: 40;
}

@media (max-width: 1200px) {
  .tool-grid { grid-template-columns: repeat(3, 1fr); }
  .tool-grid.related { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 900px) {
  .tool-grid, .form-grid, .form-grid.two, .form-grid.three, .stat-row { grid-template-columns: 1fr; }
  .nav { display: none; position: absolute; right: 28px; top: 72px; background: #134e4a;
    flex-direction: column; padding: 14px; border-radius: 12px; min-width: 180px; }
  .nav.open { display: flex; }
  .burger { display: flex; }
  .mobile-mask.open { display: block; }
  .btn-ghost { display: none; }
}
@media (max-width: 640px) {
  .container { padding: 0 16px; }
  .tool-grid, .tool-grid.related { grid-template-columns: 1fr; }
  .tool-panel { padding: 18px 14px; }
  .footer-grid { grid-template-columns: 1fr; }
}