Hello and welcome to Feedback Quest 9! My name is Hythrain, and I'm one of the hosts for this lovely event! I'm also one of the streamers, so both the game and this feedback are being done live! If you want to see the see the VOD, let me know and I'll link you to it when it's uploaded to YouTube!
There are two ways I can describe this game: multiplayer Snake OR that thing from Tron. In either scenario, it's pretty clear what you're going for. and I like it. However, I feel there are some problems in the design that should be addressed.
For starters, the warning text that pops up now and then fades away too fast before the player has a chance to read it. To make it worse, the size and colour of the text contributes to this such that, even when I'm focusing to try and read what's being said, I can't read it. Slowing the fade out speed and changing the colours to be brighter would be good ideas.
I also felt like the controls weren't always as responsive. I'd be playing and press a button to turn, only for the game to not register it and I would slam into a wall. Given the type of game this is, ultra responsive controls really matters. Now I'll admit, it's possible some of this lack of response time is due to another problem, but I'll get to that shortly.
While you have this as just a web game, you shouldn't use ESC for pausing the game or exiting a menu. If someone is playing full screen, pressing ESC will cancel their full screen first and not pause the game at all. This isn't a problem once they can download the game, but for this scenario it'd be better to not use it.
This brings me to what I thought was the bigger issue: the framerate. At times, the framerate of the game would just tank to an excessive level, going from 60 frames to less than 20 for several seconds. I couldn't pinpoint any rhyme or reason to it, it would just happen. This could be what's affecting the responsiveness, as when the framerate drops so too does the responsiveness of the controls. While a browser can affect the performance, this game isn't all that visually intensive for it to make such heavy drops happen. I'd recommend looking if there's some strange memory leaks in your code and would even suggest making a downloadable executable, as getting out of the browser could resolve a lot of this.
I also encountered some freezes, which could also be related to the framerate. I even had a freeze while in the pause menu.
Just to wrap this up, I'd like to see this have some more audio aspects to it. Since it relies on simple graphics, audio design will do a lot to give it identity. Some music and some additional sound effects would go a long way. Perhaps you could make the traces emit a sound based on the colour, so players could use those sounds to try figure out where other opponents are when they can't visually see them on the minimap.
Overall, it's a fun concept and I'd love it get fleshed out more.