COMMENT ⊗   VALID 00002 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	BEGIN "WALK"
C00003 ENDMK
C⊗;
BEGIN "WALK"
REQUIRE "DDSUB.SAI[GRA,HPM]" SOURCE_FILE;
REAL X,Y,X1,Y1,D,VX,VY,LIMIT,VV,V;
LIMIT←300;
DDINIT;
SCREEN(-LIMIT,-LIMIT,LIMIT,LIMIT);
DRKEN; RECTAN(-2*LIMIT,-2*LIMIT,2*LIMIT,2*LIMIT); INVEN;
DPYUP(-1);
RAN(CALL(0,"RUNTIM"));
VX←VY←X←Y←0;
WHILE TRUE DO
 BEGIN
 D←2*3.14159265*RAN(0); VX←VX+SIN(D); VY←VY+COS(D);
 X1←X+VX; Y1←Y+VY;
 IF ABS(X1)>LIMIT THEN X1←X1+2*(VX←-VX);
 IF ABS(Y1)>LIMIT THEN Y1←Y1+2*(VY←-VY);
 LINE(X,Y,X1,Y1); X←X1; Y←Y1;
 V←SQRT(VX↑2+VY↑2);  VV←V*(1-V/200);   VX←VX*VV/V; VY←VY*VV/V;
 DPYUP(-1);
 END;
END;