GRASS GAMES  It is free - something must have gone wrong on your system - try downloading it again to see if it helps.  
(Version 4.4)

GRASS GAMES  In the "Beginner 1" and "Beginner 2" control modes the bat is moved automatically. In the "Normal" control mode, you have to move it.

Try using the "Noral" control mode and see how you get on.  
(Version 2.32)

GRASS GAMES  I've just released version 1.41 which addresses this problem. Hopefully it will work now ok on 10.3.9.  
(Version 1.40)

GRASS GAMES  No, its a bogus virus report. Used both OSX and Stuffit to archive the (scanned and uninfected) Cubes.app program, and the resulting zip file always gets reported as having the Oversized.zip virus. It doesn't have any viruses, 100%.

You could probably reproduce this problem by unzipping the program, deleting the zip file, scanning the unzipped program (Cubes.app) to ensure its clean, and zipping it again, and (on Intel Macs anyway) it will probably still give the bogus virus warning.  
(Version 1.40)