Agreed on the legs. That walking mechanism is freaking hard. I've made some pretty nice walkers, but so far I have never managed to get anything useful out of that mechanism.
I do not understand how it works. I moved and it killed the ring it was in. I flew the little polygon into the swarm of balls, and everything either didn't collide with it or killed it. Whatever it is, it isn't fun and I don't think it works. Rated down because you did not explain it and it's confusing.
It's the twenty or so tracers that have collected over the gun, which was originally scripted by me, although fox11trot made some modifications. Those tracers are where the lag probably comes from, but I couldn't say for sure since my computer did not lag.
The scripting doesn't work, the discs don't fit very well, and after I fixed the script I found that the mechanics had a tendency to break when the disc was inserted.
Delete the file named config.cfg if you don't know how to fix the issue manually. Phun will automatically recreate a clean default config if you do that. No need to re-download.
As for the course itself, it's neat but there's a lot that can be done in terms of lag-reduction.
I'll forgive the lack of a level for it, but if you didn't build the ragdoll or guns, there is nothing else worth posting in the scene. Directional controllers are kinda lame, and that thing flies worse than anything I've ever piloted.
Add controls please - I can't tell whether it was left braking by accident or if there is some control to release it. And yes, you should edit your scenes instead of posting new ones.
Laggy and the mongoose handles terribly. Use circles instead of round polygons. Those wheels look cool but they're bouncy because polygon collisions aren't very good. I'd suggest setting the wheels you have to not collide with anything and putting invisible circles behind them.