Voidlings is the thing I keep coming back to: pick, train, and battle your own digital pet pal. Think the virtual pets you killed by accident in 1998, except this one lives in the browser and (mostly) survives you closing the tab.

The whole creature is a state machine. Hunger, energy, and mood each tick on their own timer, and the sprite you see is just a projection of those three numbers. Battles are deterministic — same inputs, same outcome — which makes them painless to test:

const dmg = Math.max(1, atk - def) * typeBonus(a.type, b.type);

Persistence is one localStorage blob plus a server-side checkpoint, so a Voidling on your phone is the same Voidling on your laptop. Next devlog: the breeding table, and why I regret the breeding table.