Changes
/* EVERY i[,t] GOSUB ln */
==== <code>EVERY i[,t] GOSUB ln</code> ====
: BASIC branches to the subroutine at line ln every i/50 seconds. (see also "AFTER i[,t] GOSUB line" for further information): Hint: Timing with interrupts is important, especially if more than one interrupts run. If the interval of a subroutine driven by an interrupt is too long than the processor can never get back to deal the main program again. Work out timing by measuring the subroutine or by trial and error.
==== <code>FILL i</code> ====