Watch Where You Are Going

In many games you need to know if something is already in the space where you are about to print another character. Whether you are firing a missile at a target, having PacMan gobble dots, or checking for a dead end in a maze, the method is the same: calculate the new position tor your moving object, check that spot on the screen before moving the character, and continue the program according to what is found in that spot. Regardless of which ZX/TS computer you are using, the theory is the same; the techniques, however, are quite different.