Why is that Wait nesseccary?

Hello, dear Scirra community!

I am trying to make a puzzle game where you should assemble certain parts of it together the right way. First of all, I tried to let pieces be picked and swapped with already picked one. I think I've done it, but I would like to know, why is that Wait action is needed in my events?

Here is my event sheet:

Also you can download the project's .capx here.

Thank you in advance!

that wait action is to give the condition and action a bit more time then the tick that c2 uses... if you disable the wait 0.01 the system will act so fast that will jump to the second condition set and the picking is not going to take place. leave it there.

Thank you, —! I thought about it a pretty similar way. I'm glad that this came out the right way to think about it )