Placing blocks terraria style? How to... what I tried?

I basically made a sprite called air and put it grid like all over the screen (invisible) So when the block is broken it adds 1 to your inventory/inventory count global variable. Then when you middle click with your mouse after everything dissapears... WHY DOES THIS HAPPEN? Any ideas?

The video you posted is privato, I am unable to see.

There is an example of .caps that does something similar, take a look at the example Turret Defense Demo Pathfinding, this puts the towers on the exact position of the grid, which you can use instead of placing towers, position the blocks by adding the sprites of these blocks take a look there how it works.