My son (9 yrs old) used plain JavaScript to make a game, and wants your feedback

This was our approach too, it worked pretty well. When Covid and the lockdowns hit it all went out the window for us. It was simply to hard to supervise the kids and work as well.

I'm glad that you have made it work for you.

Lovely!! Second this comment;

"In terms of constructive feedback: I would like to know when the various weapons are "charged." It doesn't seem like we can tell from looking.

Also it might be interesting to see what question the opponent is working on and what his answer is."

I'm skeptical too, and I started at age 10 (C64, though, not html+css+javascript).

I dunno if such skepticism is healthy or not, but looking at the source I feel that it contains too many things that need explaining to a 9yo: `DOCTYPE` and all those `META` tags correctly set when they make no difference to the game, why `box-sizing` has to be specified, all those different `display` attributes correctly set for the display that is needed for that element, what the `ease-in-out` means ...

And that's without even getting to the Javascript stuff, like why use const vs let, why use backticks and interpolation, things commented out temporarily instead of removed, the way the code is modularised, etc

In short, there are too many irrelevant-to-the-output best practices implemented that, I feel (after seeing what a lot of beginner/student programmers produce) demonstrates a level of experience that cannot come from "My First Game".

The signs of an experienced hand in the development is, to me, unmistakable.

Same. My first development environment was FutureBASIC (not counting booting an Apple ][ into the ROM's AppleSoft). The compiler error messages usually showed the right line number, the content of the line, and the where in that line something was wrong. Sometimes the real error was one line away. Rarely was the error further away. It didn't fight me about whether a new line was actually a new line.

It never told me mostly useless stuff like C, which I was exposed to a few years later. Error messages in C-ish languages seemed like they could be summarised as "Syntax error on line 247. Additionally, you have errors on 3123 other lines.". Often, the real error was on some earlier line, pages away.

The following may seem shocking to people who got started with typical programming languages, but most IDEs after my experience with FutureBASIC felt more like "a loose arrangement of parts that kinda work together if you configure them just right", rather than an _integrated_ development _environment_. (-: …Just trying to get a build environment set up or reconfigured seemed error-prone and had its own cryptic error messages. With FB, I just copied the application/executable file wherever I wanted, and copied a small folder/directory of support files to the same location. I didn't have to worry about separate "linking" and "object files", or how to tell the editing environment where the compiler was before the environment would know what to do when I told it to compile

First of all, this is great. Tell your son a guy who makes spaceships thinks it's amazing.

Constructive feedback: 1. Insight into how "smart" the opponent is via their answers to the questions they're given. 2. Charge indicators, as everyone has said. 3. From a UI perspective, centering the interface would be great, but as we all know, grown adults with PhDs in computer science have a hard time centering divs.

Great work!