The solution has been to pick the generic 'fullscreen' option, which fixes the mouse-boundary issue but adds much blurrier pixels (and messes up my Windows desktop once the game quits out). I prefer moving an RTS map via the mouse instead of arrow keys, so this issue bums me out.

This happens when you move the map around with your mouse, which is way more common in an RTS than in a Diablo game. The problem with this is the same as in Diablo: in many of the 'integer scaling' modes, WC2 lets your mouse cursor float away if pushed against the right or bottom edges. (As with Diablo, I would advise WarCraft II players to ignore these pixel-blurring options, but if that's your jam, then by all means use them.)

Instead, players can expect 'integer scaling' as an option for any monitor resolution they have so that the original artwork and sprites fall into a proper 4:3 ratio whether they appear in a window or full-screen mode. Other GOG-specific bonuses include optional anti-aliasing and anisotropic filtering. Just like this month's Diablo re-launch, GOG has rebuilt WarCraft II's executable to run with modern operating systems and monitor resolutions in mind.

Download warcraft 2 mac