Teeworlds is an online multiplayer shooter platformer game. It's extremely lightweight and has a retro vibe. Unfortunately, despite the claims the Steam page makes, Teeworlds has stopped being compiled for Windows XP since around 2018. I've compiled a custom version of v0.7.5 (latest version as of writing this) that will work on XP.
As of now only x86 builds are provided, as I couldn't get it compiling for x64. Here's a list of mirrors with the latest version.
If you're suspicious about the file, a VirusTotal scan is available.