actually i did find sliding on ice slow and was spamming wasd for the speed, i didnt see the game mention it so i assumed it was a bug mb (also i didnt see the max speed option lol, maybe it was in settings and i didnt open settings).
if you didnt notice the lag between the transitions then i think its just my pc is really old so it lagged a little bit for me (just some frame stutters, the level still loaded in like 1.5 or 2 seconds). if it doesnt lag on your pc then it probably wont lag on others either so i dont think you have to waste your time on adding multi-threading for loading levels. i will admit the screen transition looks very good though.
as for the collision bug, i was getting stuck when i had to slide between two tiles with only a one tile gap (snowballs too), i think making the player movement tiled or shrinking the collision boxes of the walls/snowballs should help
btw i saw you post your game in the weavers of infinity server (im also a member of that server now :) ) so if you want some coding assistance or just want me to send you a vid of the bugs i described, i can send it to you directly (if you are fine with it ofc)
I don't know if I'm still I'm in that particular Discord. I did jump out of a couple earlier this year for organization purposes.
But if you're able to send video of any issues you're having, then feel free to do so. Feel free to DM me on Discord if you can't find me elsewhere. Just remind me that we spoke on itch if you do DM me. Just in case I don't recognize you at first.
(And yeah it is in settings. TBH I do keep forgetting that not everyone bothers to check the settings before they play games. So that is still good to know for development purposes.)