This is very barebones, and uses the serial interface to communicate
the status of the "a" controller button being pressed.
I'd like to make this a more interactive/graphical demo.
There were two notable bugs:
- the maple transfer/data sizes were not being set correctly
- align_32byte always realigned the address of `_scene`, and not the
`mem` parameter as expected. This had the effect of the maple-DMA
send and receive buffers being the same buffer. On real hardware,
this causes unpredicable behavior.
