williams-et-al-1983-apple-ii-computer-graphics

158 APPLE II COM PUTER GRAPHICSfigures leads to 100 checks, and three figures may give you 100©! So muchfor that idea.We are going to examine two methods which both use the blind-man'scane approach. We will fi re a missile at a shape stolen from CROSSFIRE(by J. Sullivan), and as the missile moves, we will continually check itspath. The shape table is given below, so take a few minutes now to enterand save it. From BASIC type:CALL -151300 : 02 00 06 00 4A 00 4D 49308 : 49 69 18 DF DB DF DB 07310 : 48 49 69 4D 49 18 DF DB318 : DB DB 07 48 0D 6D 0D 6D320 : 0D D8 DB FB DF DB 48 09328 : 0D 0D 0D 4D 01 D8 DF FB330: DF FB 08 4D 49 4D 49 05338 : 18 DF DB DB DB 07 08 4D340 : 49 49 49 05 D8 FB DB DB348 : DF 00 36 27 0D 36 00 0BSAVE XFSHAPE, A$30,L$53 DGPOKE 232,:POKE 233 ,3HGR :HCOLOR = 3 :SCALE = l :ROT = DRAW 1 AT 2,20DRAW 2 AT 2 50The first shape is our target. It should look a bit like a spider. The secondshape is the missile, and it should look like this:xxxxxxxWhen you get the table saved correctly, you are ready to animate. Wewill leave the spider alone and move the missile back and forth across thebottom of the screen using paddle 0. When the paddle button is pressed,we will move the missile up the screen until we bump into either thespider or the top of the screen. To effect that movement, we will plot anderase the missile, then move up one line and do it again. Befo re eachmovement of the missile, we will check the space it is moving into and seeif there is something (the target) already there. Instead of checki ng to see ifsomething hits the target, we will see if something runs into the missile!We will develop the program in two stages. The following commandswill get the basic movement started. You may omit any REM statementsexcept 15© and 50© which are used as entry points for GOTO statements.