You will often want a picture of your game: for your notebook, for a task, or to show someone a bug.
A screenshot on your Mac, straight to the clipboard
Apple has a good, brief guide to taking screenshots on a Mac. Each way it describes saves a file to your Desktop. That works, but your Desktop fills up fast.
There is a better way. Add the Control key, and the screenshot goes to your clipboard instead of your Desktop. Then you can paste it anywhere, such as straight into your notebook, with Command-V.

Capture part of the screen
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Press Shift, Command and 4 together:

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The pointer turns into crosshairs
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Hold down Control, then drag across the part of the screen you want.
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Go to your notebook and press Command-V.
Capture one window
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Press Shift, Command and 4 together, then press the Space bar:

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The pointer turns into a camera
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Hold down Control, and click the window you want, such as your game’s window.
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Go to your notebook and press Command-V.
A screenshot of your game’s window
Your game runs in its own window on your Mac, so Capture one window, above, gives a clean picture of just your game.
- Press Shift-Command-4, then the Space bar, then click your game’s window.
Without Control, the picture is saved as a file on your Desktop. Drag it into your notebook, then delete it from your Desktop.
A screen recording of your game
A short video is the best way to show a game being played, or a bug that only happens sometimes.
- With your game running, press Shift-Command-5. A bar of options appears.
- Choose Record Selected Portion, and drag the box around your game’s window. Then click Record.
- Play your game.
- Click the Stop button in the menu bar at the top of the screen when you are done.
The video is saved as a file on your Desktop. Keep it short: 30 seconds is plenty.
Test of success
- Your notebook has a screenshot of your game that you pasted straight from the clipboard.
- You have made a short recording of your game, and can find the file.