TI-BASIC:Light Cycles

If you remember the old movie, Tron, you might remember the premise of this game. You control a cycle (or in this case, a pixel) that moves in a direction until you change the direction. It leaves a path, and if you hit the path, or the wall, you lose. The trick here is that you must out last your opponent: an AI. This version of Light Cycles for the calculator utilizes a simple AI system that makes it kind of intelligent. Please try to understand the code and learn from it.

The Code

:Full
:FnOff
:AxesOff
:0→Xmin:1→ΔX
:0→Ymin:1→ΔY
:ClrDraw
:Vertical Xmin
:Vertical Xmax
:Horizontal Ymin
:Horizontal Ymax
:60→A:92→B
:2→C:2→D:25→G
:Pxl-On(A,B
:Pxl-On(C,D
:Text(-1,28,31,"READY?
:Pause
:For(E,26,36
:Line(29,E,67,E,0
:End
:Repeat G=45 or not(pxl-Test(A,B) and pxl-Test(C,D
:getKey
:If Ans
:Ans→G
:A+(G=34)-(G=25→A
:B+(G=26)-(G=24→B
:1+pxl-Test(C+1,D
:Ans+(Ans=2 and pxl-Test(C,D-1
:Ans+(Ans=3 and pxl-Test(C-1,D→F
:C+(Ans=1)-(Ans=3→C
:D+(F=4)-(F=2→D
:Pxl-Change(A,B
:Pxl-Change(C,D
:End