Getting out of a cycle in a for loop

[J-M-L]

Said differently, This takes 5 seconds to execute, time during which the button is not checked at all.

@8juancho

for (int i=8;i<=12;i++){
    digitalWrite(i,HIGH);
    delay(500);
  }
  for (int i=12;i>=8;i--){
    digitalWrite(i,LOW);
    delay(500);
  }

So you need to get rid of those delays. For extra information and examples look at

• Using millis() for timing. A beginners guide
• Several things at the same time
• Flashing multiple LEDs at the same time