(this "bug" may actually be "a feature"... not sure)

In the following code, a simultaneous btn+key method is used.
I am using Player 2 "X" key for this example.

In keyconfig, set Player 2 "X" to be a key, like "\"
You should find that you can hold "\" to get a yellow line drawn on screen.
While holding that BTN down, type "c" and you should see a red circle flash on screen.

Back in keyconfig, set Player 2 "X" to be "Alt"
(I'm on Windows; I think the Mac Option key has the same behavior)

When running this sample program, hold down Player 2 "X" and the line appears as before.
Type "c" and nothing happens.

I can understand not allowing "Ctrl" (for example) but I can't think of any "would interfere with expected system operations" reason why "Alt" would have its use restricted in this way.

function _init()
   poke(0x5f2d,1)
end

function _update()
   cls()
   if btn(5,1) then
      line(0,0,127,127,10)
      if stat(30) then
         local key = stat(31)
         if (key == 'c') circfill(63,63,20,8)
         flip()
      end
   end
end