:root {
  --primary: #3b82f6;
  --primary-dark: #2563eb;
  --bg: #f5f6f8;
  --panel: #ffffff;
  --border: #e2e5ea;
  --text: #1f2937;
  --muted: #6b7280;
  --danger: #ef4444;
  --radius: 10px;
  --shadow: 0 2px 8px rgba(16, 24, 40, 0.08);
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  color: var(--text);
  background: var(--bg);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ---------- 顶栏 ---------- */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  height: 52px; padding: 0 16px;
  background: #111827; color: #fff; flex: 0 0 auto;
}
.brand { font-weight: 700; font-size: 16px; letter-spacing: 1px; }
.auth { display: flex; align-items: center; gap: 10px; }
.user-name { font-size: 14px; color: #cbd5e1; }

/* ---------- 按钮 ---------- */
.btn {
  border: 1px solid var(--border); background: var(--panel); color: var(--text);
  border-radius: 8px; padding: 8px 12px; font-size: 14px; cursor: pointer;
  transition: background .15s, border-color .15s, transform .05s; user-select: none;
}
.btn:hover { background: #f3f4f6; }
.btn:active { transform: translateY(1px); }
.btn.active { border-color: var(--primary); color: var(--primary-dark); background: #eff6ff; }
.btn.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.btn.primary:hover { background: var(--primary-dark); }
.btn.danger { border-color: var(--danger); color: var(--danger); }
.btn.mini { padding: 4px 8px; font-size: 12px; }

/* ---------- 工具栏 ---------- */
.toolbar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 8px 18px;
  padding: 8px 16px; background: var(--panel); border-bottom: 1px solid var(--border);
  flex: 0 0 auto; box-shadow: var(--shadow); z-index: 5;
}
.group { display: flex; align-items: center; gap: 6px; }
.label { font-size: 12px; color: var(--muted); margin-right: 2px; }
.tool-btn {
  width: 38px; height: 36px; border: 1px solid var(--border); border-radius: 8px;
  background: #fff; font-size: 18px; cursor: pointer;
}
.tool-btn:hover { background: #f3f4f6; }
.tool-btn.active { border-color: var(--primary); background: #eff6ff; }

.palette { display: flex; flex-wrap: wrap; gap: 5px; max-width: 320px; }
.swatch {
  width: 22px; height: 22px; border-radius: 6px; border: 2px solid #fff;
  box-shadow: 0 0 0 1px rgba(0,0,0,.15); cursor: pointer;
}
.swatch.active { outline: 2px solid var(--primary); outline-offset: 1px; }

.sizes { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.size-btn {
  border-radius: 50%; background: #444; border: 1px solid #fff;
  box-shadow: 0 0 0 1px rgba(0,0,0,.2); cursor: pointer;
}
.size-btn.active { background: var(--primary); }

/* ---------- 画板 ---------- */
#board-wrap { position: relative; flex: 1 1 auto; overflow: hidden; }
#board-container { position: absolute; inset: 0; cursor: crosshair; }
#board-container canvas { touch-action: none; display: block; }
.banner {
  position: absolute; left: 50%; bottom: 18px; transform: translateX(-50%);
  max-width: 84%; background: rgba(17,24,39,.85); color: #fff; padding: 10px 18px;
  border-radius: 999px; font-size: 14px; z-index: 6; text-align: center;
}

/* ---------- 管理面板 ---------- */
#admin-panel {
  position: absolute; top: 68px; right: 12px; width: 230px; max-height: 70%;
  overflow: auto; background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow); padding: 12px; z-index: 7;
}
#admin-panel h3 { margin: 0 0 10px; font-size: 15px; }
#admin-panel h4 { margin: 14px 0 6px; font-size: 13px; color: var(--muted); }
#admin-panel .admin { width: 100%; margin-bottom: 8px; }
.authors { list-style: none; margin: 0; padding: 0; }
.authors li {
  display: flex; align-items: center; justify-content: space-between; gap: 6px;
  padding: 4px 0; border-bottom: 1px dashed var(--border);
  font-size: 13px; overflow: hidden;
}
.authors li span { flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

/* ---------- Toast ---------- */
.toast {
  position: fixed; left: 50%; top: 64px; transform: translateX(-50%);
  background: #111827; color: #fff; padding: 10px 20px; border-radius: 999px;
  font-size: 14px; z-index: 20; box-shadow: 0 6px 20px rgba(0,0,0,.25); max-width: 80%;
}
.toast.error { background: #dc2626; }

@media (max-width: 720px) {
  .toolbar { gap: 8px; font-size: 13px; }
  .tool-btn { width: 34px; height: 34px; font-size: 16px; }
  .palette { max-width: 260px; }
}