So, thanks to the extra day, I will get to submit my almost-finished entry, yay!
But, it's painfully slow. I know that there's only so much that can be done about it - it is interpreted BASIC on a slow machine, after all!
Anyone have any top-tips for 'easy win' speedups that are still within the 'BASIC-only' rules?
E.g. fast ways of reading the keyboard, or ways of replacing slow conditionals with gotos and calculations, clever use of arrays, etc.
I'm extremely rusty with ZX BASIC - this is the first time I've used it in 30 years, and it shows! :-)