Uh.. Merge Ending? Here, I'll give you the rule for it
Go to red,
When this collides with tag #green
If (if a condition is met) a coin flip shows heads with probability __
Destroy this actor
Tell actor with tag #green
Destroy this actor
Create (I'll just say mix) in front of all actors at x 0 y 0,
Wait for __ seconds
Send player to a different card
Before all this, make a merged version of red and green, and make a merge ending card.