toolbar block icons centred in their 16px box (test for all icons), tutorials say where the objects tab is

docs/manual/tutorial-original-level.md

@@ -32,7 +32,8 @@ Every drag is one undo step – **Ctrl+Z** takes it back.
 
 ## Step 3: Add a checkpoint
 
-1. Open the **Objects** panel (left dock) and click the quick setup **Checkpoint**.
+1. Open the **Objects** tab in the left dock – the ⊙ icon right next to *Outliner* (inactive tabs show only
+   their icon) and click the quick setup **Checkpoint**.
 2. The Place tool (**P**) is now active. Click on the ground where the checkpoint should stand.
 
 The editor places a checkpoint post together with its respawn point a little in front of it.