Download some The Rainbow coco magazines online. They had a one liner contest ongoing and they printed the winners to fill dead space in the magazine. Lots of tricks there.
Some things I can think of: Compute complicated logic and do one IF then else. Traditional Microsoft basic is “unstructured” definitely no endif. Use loops even if it’s kind of inappropriate since you can have multiple loops in the same line. Tail recursion with goto. Idea is that your single conditional is at the end of the line and you go back to the same line or proceed to the next line. I think the Basic Stack is pretty limited for actual GOSUB recursion but you could try it Model 100 basic has some ability to create interrupt / events handlers. For example, on serial data. I think maybe keys and timers too. On goto / on GOSUB are good for major control flow. I don’t know if your contest has limitations on embedded ML. Of course in ml you can do any possible control flow. You can embed machine code using data statements or, more efficiently as static strings, dynamic strings or REM statements. Also there’s the ROM you can call into. — John.