If you've successfully installed Wizard 101 via Crossover on your Mac, but you see only a white screen when you actually log into the game (though you can hear music), you'll need to adjust the graphics settings on the launch screen a bit to allow the game to function on your computer's graphics hardware.
First, if you're stuck on the white screen, quit the app by holding down
command+option+QThen, launch Crossover and wizard101, again. Prior to logging in, click on the "settings" button in the login screen:
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Now,
un-check the options for "bloom active" and "fullscreen"
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Click "apply", then "ok", and then login to Wizard 101. Note that the game screen will be in a window of the size designated by the "Resolution" setting, above.