I undid too much

You pressed ⌘Z one time too many and something good disappeared.

Check these first

  1. Redo it. Press ⇧⌘Z, or click ↷ Redo in the toolbar. Each press brings back one step.
  2. Read the tooltip. Hover over ↶ Undo or ↷ Redo. It names the step, like "Undo Move object (⌘Z)". That tells you where you are.
  3. Did you make a new change after undoing? Redo only works until you do something new. Then the undone steps are gone. If so, rebuild the lost bit by hand.
  4. Was it the tutorial? If you undo a finished tutorial step, NutHouse says "Looks like that got undone. Let's do this step again." and takes you back to it.
  5. Was it saved? If the file name has no "• " in front, the last save still has it. Open the file again without saving to go back to that point.
  6. Autosave. NutHouse autosaves every 30 seconds. After a reopen, the Welcome screen can offer Get back unsaved work.
NutHouse
The Undo button tooltip naming the last step

Why it happens

Undo and redo are one list of steps. Undo walks back along it, redo walks forward. The moment you do something new, NutHouse starts a fresh branch from where you are, and the old forward steps cannot be reached any more. That is normal for every Mac app, and it is why redo straight away is the fix.

Still stuck?

Try the Chocobreak tutorial, open a sample game and read its rules, or look at the questions people ask.