Changed to use internal pull-up resistors. Chose new button and light pins for layout with self-contained illuminated buttons. Introduced use of non-blocking rtttl library. Reduced length of dedicated 'sequence' memory. Retuned notes associated with colored buttons. Switched use of Tone library to use Rtttl player. Added alternative random seeding, and used shifting to use higher-entropy bits of algorithm. Added flashing logic whilst playing tunes, including function to light all pads.