Brilliant that's great to know!! there is probably no doubt that there is room for improvements to be made in my code, but it works so that's the main thing, thank you.
Your code is great! I added PAUSE 7 in line 100 to keep it playable. In Fact ZAP and UFO where the first working game ever to compile I am still testing and fixing bugs, thanks for publishing you BASIC source codes.
tquester/ZXBasicCompiler: ZXBasic Compiler
I am really impressed what can be done in BASIC. Compiled the games not only gain speed and need a PAUSE to be playable but they also become more responsive.
I do not know how MCoder III is working, but maybe compilers do not like GOSUB f, because in compiled code, there are no line numbers. My compiler creates a symbol table if any GOTO, GOSUB or RESTORE is not a constant and calls a function to find the line and address, some games computed goto and restore for Menus or level loading.