if ... then
.....
else
.....

Program tatata;
uses sprite;//имя либы пишется без Lib
begin
//какой-то код
end;

Program asteroids;
var
nlo,asteroid,fon:image;
gameover:boolean;
over:string;
x,y:array [1..2] of integer;
begin
over:='Game Over';
nlo:=LoadImage('/nlo.png');
asteroid:=LoadImage('/asteroid.png');
fon:=LoadImage('/fon.png');
gameover:=false;
x[1]:=GetWidth/2-GetImageWidth(nlo)/2; y[1]:=20;
x[2]:=x[1]+10; y[2]:=100;
repeat
DrawImage(fon,0,0);
DrawImage(nlo,x[1],y[1]);
DrawImage(asteroid,x[2],y[2]);
y[2]:=y[2]-1;
if (y[2]=y[1]+GetImageHeight(nlo)) then begin gameover:=true end;
   if gameover=true then   
   begin   
   DrawImage(fon,0,0);   
   SetColor(255,255,255);   
   DrawText(''+(over),GetWidth/2-GetStringWidth(over)/2,GetHeight/2-GetStringHeight(over)/2);
   end;
repaint;
delay(1);
until false;
end.