You could make a bullet hell game engine as a project in an intro CS course.
The hard part is the content in the game, and ZUN was already a composer. That just leaves the code which is easy, and the bullet patterns, which ZUN clearly improved at through his earlier games. (and the art, which is famously bad though endearing)
But ZUN started on the PC-98.
To put that platform in a western context, imagine if IBM had gone with planar graphics for VGA. Or an Amiga with no coprocessors, sprites, or scrolling[0]. You have a lot of pixels to fill and no help to do it with. It can't even run DooM[1]. Most other developers threw their hands up and shipped RPGs, erotic visual novels, or porn. Getting a fast action game running on PC-98 is a genuine accomplishment.
[0] I am aware that I just described a compact Macintosh.
That very much depends on how much they did themselves. If they used unity, and went very light on the simulation, sure.
> You could make a bullet hell game engine as a project in an intro CS course.
No you couldn’t. Well you could but it wouldn’t be appropriate for actual beginners unless you stripped it down so much that calling it an engine was meaningless.
You definitely can. One of the assignments in the CS intro course I took was a bullet hell game. "calling it an engine was meaningless" is an opinion that requires ignoring the fundamentals of what a game engine is.
Let me ask you this. What were the parameters of your assignment? What libraries were you allowed to use.