mouse messages to invisible controls

[Dar Scott]

My young son is programming with Revolution.  He has card size 
images.  He wants to click on/over these and get different behavior 
depending on the zone.  He has tried invisible buttons and graphics 
but these don't seem to get mouseUp messages.

I haven't touched Hypercard for maybe a decade, it seems.  But, I 
thought there was a way to do this.

Any suggestions?

Dar Scott
Revolution Newbie