Darkspace is a virtual space where you can facilitate encrypted voice communication based on locality in the space.
There are some minimalish game engines in rust like bevy. But this still seems like too much. All we need is to render sprites in a loop and move based on keyboard input.
Vulkano and glib graphics libraries are popular but I haven't looked deeply.
This can either be server based and self-hosted for security, or else completely decentralized in a p2p gossip network. The latter will be slow and there will be lots of timing incongruencies between clients, but the demands of the vspace are not very high and some latency is fine.
p2p also means people can cheat and teleport etc. This can be a feature not a bug.
Both voip calls and position info should be e2e encrypted. Since info about location can also reveal who is talking with who.
Each user will have a local public/priv key which (pub) is shared when establishing a voice connection.
Two users can start a call by establishing a shared secret. Audio is then streamed p2p.
When a third person wants to join the conversation, all 3 people need to establish a new shared secret. When one person leaves, the remaining will establish a new shared secret. This can be done using an iterative diffie-hellman key exchange. A slower implementation would just encrypt for every person's public key.
There are also public areas where voice communication is unencrypted.