Note that https://leanprover.github.io https://leanprover.github.io is all about the frozen version of Lean 3, while the devs are working on Lean 4. In the mean

Note that https://leanprover.github.io https://leanprover.github.io is all about the frozen version of Lean 3, while the devs are working on Lean 4. In the mean time, the community is maintaining a fork of Lean 3 with some nice features + lots of docs and other material. See https://leanprover-community.github.io/ https://leanprover-community.github.io/