I'm interested in speedrunning this game and I thought are there any significant differences between the Steam and Itch.io version?
the itch.io version is just a free preview of the game - incomplete version.
No,except for the fact that Steam has some graphic updates and it has checkpoints,but either way checkpoints are useless since dying looses you time,or as dha said.
Dev here
Itch.io version is considered the free version of the game that won't be updated Steam version is basically the version of the game i am working on
You can technically do runs on both versions without issues as long as there isn't a major difference (with gameplay, levels, how bosses work etc)
We are adding new categories and subcategories later today
New categories are World 3, World 4, World 5 and Hardmode (Potential New Category could be the Calendar)
New subcategories will include all challenges in the challenges category!
Have fun!