bezier and cubic curves

[britlion]

They could be sped up by using faster trig functions, somewhat - though they would lose accuracy:
https://zxbasic.readthedocs.io/en/docs/l.../fsin.bas/

Boriel has also optimized draw and circle to be much faster than Sinclair Basic already.

Floats are also the slowest data type - you should avoid for anything you want speed for.