Hi
I am a newb myself...but I would suggest you try changing:
val = analogRead(potPin);
val = map(val, 0, 1023, 0, 25);
to something like
int valPot=0;
valPot = analogRead(potPin);
val = map(valPot, 0, 1023, 0, 25);
are you sure that is otherwise the full sketch?
daniel