if B6 = $31 and B7 < $35 then
poke B6,$32: poke B7,$35
endif
if B6 = $32 and B7 > $35 then
poke B6,$31: poke B7,$35
endif
if B6 = $32 and B7 < $30 then
poke B6,$31: poke B7,$39
endif
if B6 = $31 and B7 >$39 then
poke B6,$32: poke B7,$30
endif
goto cs