:root {
  --primary: #2468e5;
  --primary-dark: #1857c7;
  --primary-soft: #edf4ff;
  --text: #20242c;
  --text-secondary: #707783;
  --border: #e8ebf0;
  --background: #f6f7f9;
  --white: #ffffff;
  --sidebar-width: 200px;
  --header-height: 64px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  color: var(--text);
  background: var(--background);
  font-family: "Microsoft YaHei", "PingFang SC", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 14px;
  -webkit-font-smoothing: antialiased;
}

button, input { font: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
button { cursor: pointer; }

.header {
  position: fixed;
  z-index: 20;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 32px;
  background: var(--white);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 700;
  letter-spacing: .5px;
}

.brand-mark {
  width: 30px;
  height: 30px;
  display: grid;
  place-items: center;
  color: #fff;
  background: var(--primary);
  border-radius: 8px;
  box-shadow: 0 4px 10px rgba(36, 104, 229, .2);
}

.brand-mark svg { width: 18px; height: 18px; }

.top-nav { display: flex; align-items: center; gap: 12px; }

.nav-btn {
  padding: 9px 16px;
  color: #656b76;
  background: transparent;
  border: 0;
  border-radius: 7px;
  text-decoration: none;
  transition: all .2s ease;
}

.nav-btn:hover { color: var(--primary); background: #f5f8fd; }
.nav-btn.active { color: var(--primary); background: var(--primary-soft); font-weight: 600; }

.sidebar {
  position: fixed;
  z-index: 10;
  top: var(--header-height);
  bottom: 0;
  left: 0;
  width: var(--sidebar-width);
  padding: 20px 14px;
  background: var(--white);
  border-right: 1px solid var(--border);
  overflow-y: auto;
}

.category-list { display: flex; flex-direction: column; gap: 5px; }

.category-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 14px;
  color: #555c68;
  text-align: left;
  background: transparent;
  border: 0;
  border-radius: 7px;
  transition: all .2s ease;
}

.category-btn:hover { color: var(--primary); background: #f6f9ff; }

.category-btn.active {
  color: var(--primary);
  background: var(--primary-soft);
  font-weight: 600;
}

.category-count {
  min-width: 22px;
  padding: 1px 6px;
  color: #9299a5;
  background: #f1f3f6;
  border-radius: 10px;
  font-size: 11px;
  font-weight: 400;
  text-align: center;
}

.category-btn.active .category-count { color: var(--primary); background: #dce9ff; }

.sidebar-tip {
  margin: 28px 4px 0;
  padding: 14px;
  color: #7b8492;
  background: #f8fafc;
  border: 1px solid #edf0f4;
  border-radius: 8px;
  font-size: 12px;
  line-height: 1.7;
}

.sidebar-tip strong { display: block; margin-bottom: 3px; color: #4f5967; font-size: 13px; }

.main {
  min-height: 100vh;
  margin-left: var(--sidebar-width);
  padding: calc(var(--header-height) + 26px) 32px 36px;
}

.content { max-width: 1400px; margin: 0 auto; }

.search-row {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 24px;
}

.search-box { position: relative; flex: 1; }

.search-box svg {
  position: absolute;
  top: 50%;
  left: 16px;
  width: 18px;
  height: 18px;
  color: #a0a7b2;
  transform: translateY(-50%);
  pointer-events: none;
}

.search-input {
  width: 100%;
  height: 46px;
  padding: 0 44px;
  color: var(--text);
  background: var(--white);
  border: 1px solid #dfe3e9;
  border-radius: 8px;
  outline: none;
  transition: all .2s ease;
}

.search-input::placeholder { color: #9ca3af; }

.search-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(36, 104, 229, .09);
}

.clear-search {
  position: absolute;
  top: 50%;
  right: 13px;
  display: none;
  width: 24px;
  height: 24px;
  padding: 0;
  color: #8d95a1;
  background: #f0f2f5;
  border: 0;
  border-radius: 50%;
  transform: translateY(-50%);
}

.clear-search.visible { display: block; }

.section-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}

.section-heading h1 { margin: 0; font-size: 19px; font-weight: 600; }
.result-count { color: #8a919c; font-size: 13px; }

.tools-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 20px;
}

.tool-card {
  min-width: 0;
  display: flex;
  flex-direction: column;
  padding: 20px;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: 0 2px 5px rgba(24, 39, 75, .025);
  transition: transform .2s ease, box-shadow .2s ease, border-color .2s ease;
  animation: cardIn .28s ease both;
}

.tool-card:hover {
  border-color: #d7e3f7;
  box-shadow: 0 8px 24px rgba(31, 55, 90, .08);
  transform: translateY(-2px);
}

@keyframes cardIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

.tool-header {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  margin-bottom: 12px;
}

.tool-icon {
  width: 48px;
  height: 48px;
  flex: 0 0 48px;
  display: grid;
  place-items: center;
  overflow: hidden;
  color: var(--primary);
  background: transparent;
  border: 0;
  border-radius: 0;
}

.tool-icon img {
  width: 100%;
  height: 100%;
  display: block;
  object-fit: contain;
}

.tool-icon svg { width: 26px; height: 26px; }

.tool-top {
  min-width: 0;
  min-height: 48px;
  flex: 1;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 10px;
}

.tool-name { margin: 3px 0 0; font-size: 16px; font-weight: 600; line-height: 1.4; }

.tool-tag {
  flex-shrink: 0;
  padding: 3px 7px;
  color: #6e7c90;
  background: #f3f5f8;
  border-radius: 4px;
  font-size: 11px;
  font-weight: 400;
}

.tool-description {
  min-height: 42px;
  margin: 0 0 14px;
  color: var(--text-secondary);
  font-size: 13px;
  line-height: 1.65;
}

.tool-meta { display: flex; align-items: center; flex-wrap: wrap; gap: 7px; margin-bottom: 18px; color: #8a919c; font-size: 12px; }
.meta-dot { width: 3px; height: 3px; background: #c0c5cd; border-radius: 50%; }

.download-btn {
  width: 100%;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 7px;
  margin-top: auto;
  color: var(--white);
  text-decoration: none;
  background: var(--primary);
  border: 0;
  border-radius: 7px;
  font-weight: 500;
  transition: background .2s ease, box-shadow .2s ease;
}

.download-btn:hover { background: var(--primary-dark); box-shadow: 0 4px 12px rgba(36, 104, 229, .22); }
.download-btn:active { transform: translateY(1px); }
.download-btn svg { width: 15px; height: 15px; }

.empty-state {
  display: none;
  padding: 76px 20px;
  color: #8a919c;
  text-align: center;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: 10px;
}

.empty-state.visible { display: block; }
.empty-icon { margin-bottom: 12px; font-size: 38px; opacity: .65; }
.empty-state h3 { margin: 0 0 8px; color: #4d5562; font-size: 16px; }
.empty-state p { margin: 0; }

.page-footer { margin-top: 28px; color: #9aa1ab; font-size: 12px; text-align: center; }

.toast {
  position: fixed;
  z-index: 100;
  left: 50%;
  bottom: 30px;
  padding: 11px 20px;
  color: #fff;
  background: rgba(28, 33, 41, .92);
  border-radius: 7px;
  box-shadow: 0 6px 22px rgba(0, 0, 0, .16);
  opacity: 0;
  transform: translate(-50%, 12px);
  pointer-events: none;
  transition: all .25s ease;
}

.toast.show { opacity: 1; transform: translate(-50%, 0); }

@media (min-width: 1500px) {
  .tools-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

@media (max-width: 1050px) {
  .tools-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .main { padding-left: 24px; padding-right: 24px; }
}

@media (max-width: 720px) {
  :root { --header-height: 58px; }
  .header { padding: 0 16px; }
  .brand { font-size: 16px; }
  .brand-mark { width: 28px; height: 28px; }
  .top-nav { gap: 2px; }
  .nav-btn { padding: 8px 9px; font-size: 12px; }
  .top-nav .nav-btn:first-child, .top-nav .nav-btn:last-child { display: none; }
  .sidebar {
    top: var(--header-height);
    right: 0;
    bottom: auto;
    width: auto;
    padding: 10px 12px;
    border-right: 0;
    border-bottom: 1px solid var(--border);
    overflow-x: auto;
  }
  .category-list { flex-direction: row; width: max-content; gap: 4px; }
  .category-btn { width: auto; gap: 8px; padding: 9px 12px; white-space: nowrap; }
  .sidebar-tip { display: none; }
  .main { margin-left: 0; padding: calc(var(--header-height) + 76px) 16px 24px; }
  .tools-grid { grid-template-columns: 1fr; gap: 14px; }
  .tool-description { min-height: auto; }
  .search-row { margin-bottom: 18px; }
}