The beta has been updated. Fixes since the last beta include:
Mouse handling robustness improved; mouse drift on puzzle screen should be gone.
More-robust selection of fullscreen display modes. Fall back to windowed mode if a fullscreen mode cannot be found.
In windowed mode, the window can be resized.
(Note: -width and -height arguments will not currently affect fullscreen mode; they only affect windowed mode).
Hopefully runs on Windows XP again (not yet tested locally, but if someone out there could try it, that would be great).