:root {
  --bg: #f4f7fb;
  --surface: #ffffff;
  --text: #111827;
  --muted: #64748b;
  --line: rgba(15, 23, 42, .12);
  --primary: #2563ff;
  --primary-dark: #1747c7;
  --danger: #dc2626;
  --shadow: 0 18px 48px rgba(15, 23, 42, .08);
}

* { box-sizing: border-box; }

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  background: var(--bg);
  font-family: "PingFang SC", "Microsoft YaHei", "Segoe UI", Arial, sans-serif;
}

button, input, select { font: inherit; }

.app-shell {
  width: min(1440px, calc(100% - 28px));
  margin: 0 auto;
  padding: 16px 0 28px;
}

.topbar {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  gap: 18px;
  align-items: center;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.back-link {
  color: var(--primary);
  font-size: 14px;
  font-weight: 700;
  text-decoration: none;
}

.title-block h1 {
  margin: 0;
  font-size: 24px;
  line-height: 1.2;
}

.title-block p {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.6;
}

.top-actions {
  display: flex;
  gap: 10px;
  align-items: center;
}

.button, .tool, .mini {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 38px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--text);
  font-weight: 750;
  cursor: pointer;
}

.button.primary {
  color: #fff;
  border-color: var(--primary);
  background: linear-gradient(180deg, var(--primary), var(--primary-dark));
}

.button.secondary {
  color: var(--primary);
  border-color: rgba(37, 99, 255, .22);
}

.button:disabled, .mini:disabled, .tool:disabled {
  cursor: not-allowed;
  opacity: .45;
}

.notice {
  display: flex;
  gap: 10px;
  margin: 14px 0;
  padding: 12px 14px;
  border: 1px solid rgba(37, 99, 255, .18);
  border-radius: 10px;
  background: #eef5ff;
  color: #1e3a8a;
  font-size: 14px;
  line-height: 1.6;
}

.workspace {
  display: grid;
  grid-template-columns: 180px minmax(0, 1fr) 230px;
  gap: 14px;
  align-items: start;
}

.sidebar, .editor-panel, .help-panel {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  box-shadow: var(--shadow);
}

.sidebar, .help-panel {
  padding: 14px;
}

.side-head {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
}

.page-list {
  display: grid;
  gap: 8px;
  margin-top: 12px;
}

.page-item {
  display: flex;
  justify-content: space-between;
  width: 100%;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  cursor: pointer;
}

.page-item.active {
  color: #fff;
  border-color: var(--primary);
  background: var(--primary);
}

.empty-side {
  color: var(--muted);
  font-size: 13px;
  line-height: 1.6;
}

.editor-panel {
  overflow: hidden;
}

.toolbar, .settings {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  padding: 12px;
  border-bottom: 1px solid var(--line);
}

.tool.active {
  color: #fff;
  border-color: var(--primary);
  background: var(--primary);
}

.tool.danger {
  color: var(--danger);
}

.settings label {
  display: inline-flex;
  gap: 8px;
  align-items: center;
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}

.settings input[type="number"] {
  width: 72px;
}

.settings input, .settings select {
  height: 34px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 0 8px;
  background: #fff;
}

.pager {
  display: inline-flex;
  gap: 8px;
  align-items: center;
  margin-left: auto;
  color: var(--muted);
  font-weight: 800;
}

.canvas-shell {
  position: relative;
  min-height: 620px;
  padding: 18px;
  overflow: auto;
  background: #dbe3ef;
}

.canvas-shell.empty {
  min-height: 620px;
  cursor: pointer;
  pointer-events: auto;
}

.canvas-shell.editing {
  display: flex;
  justify-content: center;
  align-items: flex-start;
  min-height: 0;
  cursor: default;
}

.canvas-shell.dragover {
  outline: 3px solid rgba(37, 99, 255, .35);
  outline-offset: -8px;
}

.upload-state {
  display: grid;
  place-items: center;
  align-content: center;
  gap: 8px;
  min-height: 560px;
  border: 1.5px dashed rgba(37, 99, 255, .32);
  border-radius: 12px;
  background: #fff;
  text-align: center;
  color: var(--muted);
  cursor: pointer;
  pointer-events: auto;
}

.upload-state strong {
  color: var(--text);
  font-size: 20px;
}

.page-stage {
  position: relative;
  width: max-content;
  margin: 0 auto;
  background: #fff;
  box-shadow: 0 16px 42px rgba(15, 23, 42, .24);
}

#pdfCanvas, #editCanvas {
  display: block;
}

#pdfCanvas {
  position: relative;
  z-index: 1;
  pointer-events: none;
}

.page-stage .canvas-container {
  position: absolute !important;
  left: 0 !important;
  top: 0 !important;
  z-index: 2;
}

#editCanvas, .upper-canvas, .lower-canvas {
  position: absolute !important;
  left: 0 !important;
  top: 0 !important;
}

.upper-canvas {
  pointer-events: auto;
}

.help-panel h2 {
  margin: 0 0 10px;
  font-size: 18px;
}

.help-panel p {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.6;
}

.status {
  margin-top: 12px;
  padding: 10px;
  border-radius: 8px;
  background: #f8fafc;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.6;
}

@media (max-width: 1100px) {
  .workspace {
    grid-template-columns: 150px minmax(0, 1fr);
  }

  .help-panel {
    grid-column: 1 / -1;
  }
}

@media (max-width: 760px) {
  .app-shell {
    width: min(100%, calc(100% - 14px));
  }

  .topbar {
    grid-template-columns: 1fr;
  }

  .top-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
  }

  .workspace {
    grid-template-columns: 1fr;
  }

  .sidebar {
    order: 2;
  }

  .editor-panel {
    order: 1;
  }

  .help-panel {
    order: 3;
  }

  .toolbar {
    flex-wrap: nowrap;
    overflow-x: auto;
  }

  .tool {
    flex: 0 0 auto;
  }

  .settings {
    align-items: flex-start;
  }

  .pager {
    width: 100%;
    margin-left: 0;
  }

  .canvas-shell {
    min-height: 460px;
    padding: 10px;
  }
}