Help understanding Move safely

I am trying to understand how to use the move safely object.
In the test case below, I want the top red and green boxes to stop at the edge. While the bottom red and green boxes should stop when colliding with each other.

I've attached my mfa file where the app crashes once the red and green boxes collide (move by holding space).

What is the best way to solve this?

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Quote from Fadzior

Here

Niiice! Thank you

Quote from Fadzior

Here

It seems to work great in that small test case, but it still is not working fully when applying it to my project.

I am using the platform movement object for the player and the enemy movement and want to make sure they never overlap each other, as it does here:

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I've attached a new test case which includes PMO