Car appreciation... the aesthetics, the engineering, etc

I wonder what the least power you could have fun with is, if you made a really, really light car?

i.e. a carbon chassis, two seats, narrow and light wheels etc etc with (say) a 300cc twin cylinder, or perhaps even smaller?

The old Caterhams with under 200 bhp were pretty lively!

Classic Mini with 1000cc motorbike engine is very lively.