I'm planning to not do diagonal surfaces, just regular ones. I realized portal bumping would be an issue but haven't put much thought into that yet to be honest. I'm thinking I'll solve it by making the portals snap to the 5x5 grid automatically and simply check if the variable containing the existing portal is the same as the variable containing the portal that's being placed.

My biggest problem will probably be speed and size.

Thank you Builderboy if my game ends up being half as good as yours, I'll be happy.

Here's what I've got for a menu (also added to first post):

Thank you Builderboy if my game ends up being half as good as yours, I'll be happy.

Here's what I've got for a menu (also added to first post):

That menu is epic.

I'M a bit late to the party, but I was surprised to see a new portal game being worked on. If you can somewhat match the original Portal Prelude physics and gameplay it will be amazing. It's already a big classic for calcs so I'm sure people would be happy to see a sequel (assuming it gets finished of course, although if you decide to not finish this, a level pack for Portal Prelude instead would still be kinda cool).

Something I wonder: Builderboy originally made one or two Portal games in pure BASIC before he started the Axe game. Do you think the levels from the BASIC game could be implemented into a new Axe Portal?

If you can somewhat match the original Portal Prelude physics and gameplay it will be amazing.

That's the plan    It will have an entirely different plot and a few different features (most likely swapping out energy pellets for something else as they weren't included in Portal 2), but I plan on making it overall similar to Builderboy's (especially graphically). As for the BASIC levels, that's not a bad idea.

Update: I've had little time with classes and everything to work on this lately, but I still made some progress. Portals can now be shot (up and down only, more to come later). I also wrote decent code that let the player fall through the portals but it got deleted... I plan to rewrite it this weekend.

Aw didn't show any screenshots of the dude going through the portal?  Also it looks like you are planning to have the portals 5 pixels wide, what made you decide to use those dimensions?