How to unlocke other worlds?

[Perfect Thoughts]

I completed all the new and original levels in world 1, I played in world 2, but when i leave the game I can't choose any worlds exept the first one.

I know that this is probably a stupid question, I can't figure it out by myself cause I wan't to play as little as possible cause this game makes me motion sick. I just want all the achievements.

[Cherno]

You need to drag the world list with the mouse (or use the shoulder buttons if you use a controller).

[Cherno]

Is a really really weird design choice... not intuitive at all.

[jAsZcZuRkA]

try F1, works too

[JennKhatte]

F1 works fine