If you have a Mac with the integrated Intel HD 4000 graphics card, DO NOT up the default graphics settings from Low to Medium/High. Your game will become unplayable. Leave them as Low until EA releases a patch to fix this.
If you have already upped the settings and cannot now play your game just dump your Options.ini file onto your desktop, the game will recreate a new one and you should be good to go. You can find the Options.ini file here:
Documents > Electronic Arts > The Sims 4
Update – some users are reporting that after upgrading to Yosemite their games are running properly on higher settings with the Intel HD 4000.