What baffled me most about that time, was that (some) developers would use PCs to develop ZX spectrum games. This was e.g. described in Bob Papes fantastic book

What baffled me most about that time, was that (some) developers would use PCs to develop ZX spectrum games. This was e.g. described in Bob Papes fantastic book "It's behind you", where he recalls the development of R-Type. Nowadays you would definelty do so, and you still can, e.g. with using C with z88dk and target a whole palette of Z80 targets.