The triangles are a result of the print "wall" changing thickness. Look at the corner on the left. All 10 perimeter lines go all the way round. If 10 go in and 10 come out, we need extra perimeter lines in the corner to fill the extra width. That's why there are triangles.
I imagine you could fix this by making the walls the same thickness at all points, but without trying I can't be sure.
I like that it's not a fully enclosed design, those always feel like they're not making the best use of the printing process.
A fillet on each of the vertical edges should help with any warping on the main body. Adding a brim if you haven't already will also help.
I'm away from my printer for a couple of weeks, but when I get back I'm definitely going to be printing one of these. Thanks for sharing!
I've not played Cult of the Lamb but Hades had the same effect on me. Love that game.
I'd suggest loosening all the bed screws as much as is practical and then redoing the mesh. That way you've got lots of room to lower high spots.
If the tilt is too extreme, you might also be dealing with a sagging gantry. I'm not familiar with your printer model so I don't know how likely that is or how you'd go about fixing it though I'm afraid.
It depends on the brand. The shop I get mine from still uses plastic for their in-house brand but apparently they're looking into switching to cardboard.
The other solution I like is selling reusable spools that come in half so you can load new rolls of filament on them. Even less waste!
Good Job was a lot of fun. I played it with my daughter when she was about that age.
I have an Ender 3 V2 that I barely ever print on any more because I have a RatRig V-Minion now. I love this little monster, it's so fast.