How to create a Mario Style jump block?

I know there was a conversation already about this, but I couldn’t find it. SO, I need a block that is transparent when going through from the bottom of it, but solid when coming in from the top.
Drawing (14)

Ah, I see what you are trying to create: a semisolid platform/block. @“JR 01” made an example game all about the two main methods to create such blocks. Right here is a link to the discussion where he posted that example game.
(I didn’t want to post a link to the example game because I didn’t want to seem like I was stealing from other people.)

Thank you!