An Arduino pin can power 1 LED, but not 18 at the same time. You need a transistor to operate so many LEDs, or one pin for each button. As pin 13 already powers the on-board LED, you also should use a different pin for your buttons.
An Arduino pin can power 1 LED, but not 18 at the same time. You need a transistor to operate so many LEDs, or one pin for each button. As pin 13 already powers the on-board LED, you also should use a different pin for your buttons.