Mynah 1.2.0

Mynah v1.2.0 — simulator and command history

The hosted copy now runs a built-in simulator rather than offering a connection
that cannot work, with a banner saying so. Four screens, layers, three preset
buffers each, and a wireframe of what every screen is putting out.

It reproduces the device behaviour worth learning before you meet hardware: a
recall of an empty memory is answered with silence, and a Take visibly swaps
which buffer is preview and which is program.

Command history walks with the up and down arrows.