I've been building this together with my daughter for about six months. The battlefield is generated each match from a Delaunay triangulation + Lloyd relaxation - 3 iterations gave the best balance between chaotic and grid-like maps (more relaxation makes it too uniform and predictable, less makes it a mess of tiny isolated clusters). Core mechanic is flood-fill capture: click a cell, claim every connected same-colored crystall. On top of that there're supply lines (cut a region off from itsbase and it becomes vulnerable to instant mass capture), bombs that chain-react and permanently reshape the map, energy crystals for bonus turns and obstacles like lakes and mountains. Stack: TypeScript + Canvas, no game engine, d3-delaunay for the map generation, Socket.IO for multiplayer.

Free to play in browser, no install, no account: https://play.crystalwars.io There's also a full paid version on Steam with the full campaign and some more custom options, like palettes, presets and textures, if you want to support it: store.steampowered.com/app/4810920

Happy to talk about anything in the game.