Help identify an Asteroids clone

[Kosashi]

There's a clone of Asteroids which I've been seeking for years. I played it like 5-8 years ago and it's probably older than that.

I remember that:

- I ran it on Windows
- it had colorful vector graphics, i.e. symbolic outlines made of lines, something like the image below
- it was very rich in content; many different types of enemies, probably also obtainable weapons
- every 5 (or so) levels there was always a random "special encounter" level, which didn't contain normal asteroids, but a different challenge to beat (of which there was a nice variety).


The game was full of nice ideas and probably the best remake that I've played (even though I've played quite a few). I'd be really glad to see it again. Any ideas?