I've triple-checked. It's exactly this:
:FnOff
:ClrHome
:ClrDraw
:GridOff
:AxesOff
:PlotsOff
:0→Xmin:1→∆X
:0→Ymin:1→∆Y
:20→G
:For(X,0,47
:Vertical X
:Line(X,Ans,X,Ans+G,0
:Ans+randInt(-(Ans>2),Ans<53-G
:End
:Ans→X:-1→A
:31→B:.2→F
:For(θ,0,E9
:Text(0,0,θ
:If not(fPart(A/3
:Pt-Off(C,D
:Pt-On(A,B
:A→C:B→D
:getKey→E
:F-.1+.3(Ans=21→F
:B+Ans→B
:(A+1)(A≠Xmax→A
:G-.5not(Ans→G
:A+47-95(A>47
:Pt-On(Ans,X+randG,1+not(fPart(θ/32
:Vertical Ans
:Line(Ans,X,Ans,X+G,0
:X+randInt(-(X>2),X<53-G→X
:G-not(A→G
:If E=105:Pause
:If not(E=45 or pxl-Test(Ymax-round(B,0),A
:End
:For(C,1,9
:Pt-Change(A,B
:rand(20
:End
:ClrHome
:ClrDraw
:Disp "Distance:
:Output(1,10,θ
into my TI-83 Plus. The "E9" is an exponent E.
