Cannot go downstairs (keyboard input problem on Linux)

I'm unable to go downstairs in e.g. `cargo run` inside chapter-21-rexmenu.

My experiments with glutin's `cargo run --example window` show that when I press the period key on my keyboard, the events look like this:

```
WindowEvent { window_id: WindowId(Wayland(WindowId(94351912379904))), event: KeyboardInput { device_id: DeviceId(Wayland(DeviceId)), input: KeyboardInput { scancode: 52, state: Pressed, virtual_keycode: None, modifiers: ModifiersState { shift: false, ctrl: false, alt: false, logo: false } } } }
WindowEvent { window_id: WindowId(Wayland(WindowId(94351912379904))), event: ReceivedCharacter('.') }
```

I've no idea why virtual_keycode is None. Bug in glutin maybe?

I'm wondering if maybe ReceivedCharacter would be a better event to use for character-based input commands? Might it work better for people using non-QWERTY keyboard layouts? (I wonder how Dvorak users like to play roguelikes?)