A pad instrument.
- Add sound type menu.
- Add layouts.
- Add menu to change pad size.
- Layout pads.
- Decide layout syntax.
- row
- column
- size
- Parse layout string.
- Write layout css.
- Write pads html.
- Handle events.
- Add event callbacks to the board.
- touchstart.
- touchend.
- touchmove.
- touchcancel.
- Change pad colors.
- Sound notes.
- Convert note string to note id.
- Create a oscillator when a pad becomes active and start it.
- Stop the oscillator when the pad becomes inactive and forget it.
- Use hidden div for note layout.