But looking at the source, the weird part is that it is half English, half French. It definitely doesn't look like the work of a single person.
I also looked at the commit history and I liked the teaching comments.
Clearly, there is a story behind that code. I suspect you did the first part together (moving square, ...) and that your brother played with it by himself later, adding the enemy, etc...
Funny story from ~2005, a company developed a jvm for a special cpu and was aquired by a bigger company. After the aquasition 2 developers had to search the code base for two weeks after swedish swear words, they replaced them with the word of dandelion in swedish ("maskros").
What I want to say is that it is very common to mix english and ones native language.
I've also seen the native word to avoid conflicts, like adding "2" at the end of a variable. That's bad, don't do it kids ;)
But here, the "hero" has a "speed" while the "ennemi" (french for "enemy") has a "vitesse" (french for "speed"). That's why I thought that the enemy is more likely to be a later, less supervised addition.
And BTW, I didn't notice any french swear word in that code. That kid is more mature than I was :)