I have a working game! Lots of features aren't implemented yet, like scoring and auto clearing areas, but it works! I learned some interesting tricks to reduce the memory size. One of the most novel I found online is for moving a cursor:
20 LET Y=Y+(INKEY$="6")-(INKEY$="7") 25 LET X=X+(INKEY$="8")-(INKEY$="5")
This little snippet replaces 4 lines of normal IF, THEN code by taking advantage of the fact that the INKEY$ comparison resolves to 1 or 0. Adding and subtracting the result for the various keys moves the stored cursor coordinates. I have to say, I really like the Sinclair implementation of BASIC. It has some printing and comparison features that are lacking in Applesoft BASIC. However, the only thing that made programming bearable was writing out the entire program before trying to enter it. Data entry and minor editing is not too bad, but trying to think out a program on the TS1000 is not fun. I will make the source and a download available shortly.