how long did it take to learn wasm
I actually did not write any pure wasm code. I wrote the whole game in c++ and then compiled it to wasm, as you would normally do.
However, I used wasm-4 library (as this is a wasm-4 game jam entry), which took care of drawing the framebuffer and playing sounds for me. Since the library is very simple, I did not have any problems doing stuff right away.