Alright, so I'm making tiles, making it so that they're collidable but not portalable, putting it in the template, blah blah blah, and when I put them into the game, doing exactly as this forum says, and placing them down, I test the level and Mario falls through the blocks. Here's the file. It's not complete, but it's what I have:
Here's the dirt block that's working properly:
, and here's one that's not working right;
What am I doing wrong?