This one is not for a grade. There is no dropbox, no deadline, and nobody checking. It is here because Lua is a genuinely fun language and it is small enough to actually finish.
Unit 1 teaches the language itself — plain Lua, one file, run from a terminal. Unit 2 uses it to build a game in LÖVE, a framework people ship real games with. The order matters: LÖVE is easy to use without ever learning Lua, and a person who does that ends up able to finish a game but not read a Lua file.
You should already have written a little code in something — any language. If you know what a variable and a loop are, you have enough. This course spends its time on what makes Lua different, not on what a loop is.
None of these are needed for Unit 2. They are here because they are the parts of Lua people find most interesting.