what would the logic /python look like?
Im guessing you mean mouselook?
Google is your friend, and so is the search on this forum, there are a few different ways to do it, but one of the easiest and most flexible comes from this site:
The mouselook is about half way down - http://www.tutorialsforblender3d.com/Game_Engine/Tutorials_index.html
Search this forums as well, theres a few other versions around which are a bit different.
i mean make blocks disappear when you click them
You would need a mouse over and a mouse click sensor hooked up to a python script, that python script would then get what is underneath the mouse and delete it. However I’m not aware if a command to get what is underneath the mouse exists.
have a mouse over and mouse click sensors connected to an and controller, which is connected to an end object actuator. put this on each cube.