:root {
  --bg: #f7f8fb;
  --panel-bg: #ffffff;
  --border: #e5e7eb;
  --text: #1f2937;
  --muted: #6b7280;
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --accent: #ec4899;
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 4px 12px rgba(0,0,0,0.04);
  --radius: 10px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", Roboto, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 16px; }

/* 顶部广告位 */
.ad-slot {
  width: 100%;
  background: linear-gradient(90deg, #eef2ff, #fdf2f8);
  border-bottom: 1px solid var(--border);
}
.ad-top { min-height: 90px; display: flex; align-items: center; justify-content: center; }
.ad-inner { color: var(--muted); font-size: 13px; padding: 8px 12px; text-align: center; }
@media (max-width: 768px) {
  .ad-top { min-height: 60px; }
}

/* 头部 */
.site-header { background: var(--panel-bg); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 50; }
.header-row { display: flex; align-items: center; justify-content: space-between; height: 60px; gap: 12px; }
.logo { display: flex; align-items: center; gap: 8px; text-decoration: none; color: var(--text); font-weight: 700; font-size: 18px; }
.logo-mark { width: 32px; height: 32px; background: var(--primary); color: white; border-radius: 8px; display: grid; place-items: center; font-weight: 700; }
.header-nav { display: flex; gap: 18px; }
.header-nav a { color: var(--muted); text-decoration: none; font-size: 14px; }
.header-nav a:hover { color: var(--primary); }

/* Tabs */
.tabs {
  display: flex;
  flex-wrap: nowrap;
  overflow-x: auto;
  gap: 4px;
  padding: 8px 16px;
  border-top: 1px solid var(--border);
  scrollbar-width: thin;
}
.tab {
  flex: 0 0 auto;
  padding: 8px 14px;
  border-radius: 8px;
  text-decoration: none;
  color: var(--muted);
  font-size: 14px;
  white-space: nowrap;
  border: 1px solid transparent;
  transition: all .15s ease;
}
.tab:hover { background: #f1f5ff; color: var(--primary); }
.tab.active { background: var(--primary); color: white; }

/* Main */
.main-area { padding: 24px 16px 60px; }
.panel {
  background: var(--panel-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}
.panel h1 { margin: 0 0 8px; font-size: 24px; }
.panel .lead { color: var(--muted); margin: 0 0 20px; }

.tool-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  align-items: start;
}
.tool-grid.two-col { grid-template-columns: 1fr 1fr; }
.tool-grid > .preview { grid-column: 1 / -1; }
@media (max-width: 860px) {
  .tool-grid, .tool-grid.two-col { grid-template-columns: 1fr; }
}

/* Dropzone */
.dropzone {
  border: 2px dashed #c7d2fe;
  border-radius: var(--radius);
  padding: 36px 16px;
  text-align: center;
  cursor: pointer;
  transition: all .15s ease;
  background: #fafbff;
  color: var(--muted);
}
.dropzone:hover, .dropzone.drag { border-color: var(--primary); background: #eef2ff; color: var(--primary); }
.dropzone p { margin: 0; }

/* Controls */
.controls { display: flex; flex-direction: column; gap: 10px; }
.controls label { display: flex; flex-direction: column; gap: 4px; font-size: 14px; color: var(--text); }
.controls label > span { color: var(--muted); }
.controls input[type="number"], .controls input[type="text"], .controls select, .controls textarea, textarea {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 14px;
  font-family: inherit;
  background: white;
}
.controls input[type="range"] { width: 100%; }
.controls fieldset { border: 1px solid var(--border); border-radius: 8px; padding: 10px 12px; }
.controls fieldset legend { padding: 0 6px; color: var(--muted); font-size: 13px; }
.controls fieldset label { flex-direction: row; align-items: center; gap: 6px; margin: 4px 8px 4px 0; }

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 8px 14px; border-radius: 6px; border: 1px solid var(--border);
  background: white; color: var(--text); cursor: pointer; font-size: 14px;
  text-decoration: none; transition: all .12s ease;
}
.btn:hover { border-color: var(--primary); color: var(--primary); }
.btn-primary { background: var(--primary); color: white; border-color: var(--primary); }
.btn-primary:hover { background: var(--primary-hover); color: white; border-color: var(--primary-hover); }
.btn-ghost { background: transparent; }
.btn-row { display: flex; flex-wrap: wrap; gap: 6px; }

/* Preview */
.preview { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-top: 12px; }
@media (max-width: 720px) { .preview { grid-template-columns: 1fr; } }
.preview-item { background: #f9fafb; border: 1px solid var(--border); border-radius: 8px; padding: 12px; text-align: center; }
.preview-item.full { grid-column: 1 / -1; }
.preview-item h4 { margin: 0 0 8px; font-size: 13px; color: var(--muted); font-weight: 500; }
.preview-item img, .preview-item canvas { max-width: 100%; height: auto; display: block; margin: 0 auto; border-radius: 6px; }
.preview-item span { display: block; margin-top: 6px; font-size: 12px; color: var(--muted); }

.canvas-wrap { background: #f9fafb; border: 1px solid var(--border); border-radius: 8px; padding: 8px; overflow: auto; max-width: 100%; }
.canvas-wrap canvas { max-width: 100%; cursor: crosshair; }

textarea { resize: vertical; }
img#b64-preview { max-width: 100%; margin-top: 10px; border-radius: 6px; }

/* Howto */
.howto {
  margin-top: 28px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}
.howto h2 { font-size: 16px; margin: 0 0 10px; }
.howto ol { padding-left: 22px; color: var(--muted); }
.howto ol li { margin: 4px 0; }

/* Footer */
.site-footer { background: #111827; color: #d1d5db; padding: 36px 0 20px; margin-top: 40px; }
.footer-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; padding: 0 16px; }
.footer-grid h3 { color: white; font-size: 15px; margin: 0 0 8px; }
.footer-grid p { color: #9ca3af; font-size: 13px; margin: 0; }
.copyright { text-align: center; color: #6b7280; font-size: 12px; margin-top: 24px; padding: 0 16px; }
@media (max-width: 720px) { .footer-grid { grid-template-columns: 1fr; } }