This is what I have so far, showcasing the main mechanic of the game. Obviously this has been done thousands of times before, but meh, I had no other idea so I'm going with this. I will probably prevent the player from changing between day/night and make it more puzzle-based, so that you have to use switches and such (that way I dont even have to fix how you can get stuck inside blocks as shown near the end of that gif). Right now, blocks can be either always active, or only active during day or night.
With more blocks and stuff in the bg, the shift between day and night wont be as epilepsy-inducing, as well. I want to add grey stuff so that'll be more easy on the eyes. I also have other block sprites ready.
And then optimization. Despite a
minimum of 4 instance_place calls per frame, this is rocking a solid 60fps min, depending on what applications I have open it goes up to 200 min. Very positively surprised by that. There is no optimization whatsoever, and I'm even using a for loop for horizontal and vertical movement when hitting a wall instead of move_contact_solid, which I've found in other platforming engines, is faster for this stuff. But idk if I can make it use that instead, in my implementation. I'll see. (EDIT2/update: I can't currently make it use move_contact_solid without entirely changing how I check collisions, which I don't plan to do anyway, not this early at least. And yes, the gif is at 24fps because I reset my sharex settings a few days ago)
As for music and sfx, there's still nothing. I'll probably take a little break and design some puzzles.
EDIT: also ignore that in my gif, you can jump three blocks high so the entirety of the time I'm switching day/night to jump on the blocks on the left, I dont have to because the ones that are on the wall are still possible jumps lol
EDIT3: at least if I dont finish it I still have something to submit: a decent platforming engine with an interesting mechanic