Mindustry: A open-source sandbox tower defense game (github.com)

The project is quite impressive. It's not old-school tower defense as the title might suggest. This is a complex base building and resource processing simulation game similar to Factorio. It is implemented in clean Java and runs smoothly on both desktop and mobile platforms. It has a full campaign, competitive multiplayer and a dedicated reddit community.

Any screenshots?

It’s really good. Costs money on Steam but is much easier to do multiplayer then, which is really where the game shines in my opinion.

I've installed it on android and nixos. The touch controls on android are a little finicky. Better to play on desktop with keyboard+mouse.

Pretty addictive for most of the campaign! I wonder how it plays in multiplayer?

This game single handedly justifies my phone's stylus. Without it playing on android is a bit fiddly. Works great on a chromebook with keyboard and mouse though.