How to stop overlapping objects

[fishrod]

So when i hold left mouse button it creates grass tiles.
I move around with the mouse and stays making grass tiles works fine.
Just one problem it also creates grass tiles ontop of other grass tiles.
How i stop the game creating grass tiles on top of eachother?
Thanks!

[Danny]

Add a new condition to your create event...

+Grass Tile is overlapping another object (or grass tile)[NEGATE]

[fishrod]

I did this also tried some other things with negate.
Tiles still overlaps but when the first 2 tiles are overlapping i can't place more tiles.
So is there another solution?
Btw thanks for telling me about negate really helps with some other bugs in the game.

[Danny]

Ah, best to create an 'invisible' placeholder underneath your mouse which you can use as a 'detector'. You can make the object invisible and have it follow the mouse:
Always: Set X Position (XMouse) / Y Position (YMouse)

Then check to ensure that isn't overlapping!