#TI-BASIC, 71
1->A 1->B 1->C 1->D While 1 ClrHome Output(B,A,"O A+C->A B+D->B If A<2 or A>15 ~C->C If B<2 or B>7 ~D->D End Quite literal translation, I wouldn't be surprised if there are tricks to make it smaller.
The screen is 16x8 and 1-indexed so the constants are different.
~ is the SourceCoder way to write the negation symbol.
It looks smoother on hardware.