So I recently downloaded the custom 2003 beta build for Half-Life: Source done by Half-Life Project Beta, but I think it needs to be updated. The mouse behavior is extremely buggy and will often bolt to wherever it wants. This is likely due to a Windows update from some months back which also affected the mouse movement for games such as Half-Life, Half-Life 2, Quakespasm, and more. That aside, HLPB's build of the HL:Source beta is also unable to go into fullscreen. If you uncheck "run in a window" it automatically becomes checked again.
EDIT: Upon further inspection, there's more bugs than just the ones I mentioned. Saving doesn't work, poor mouse-click detection, some some weird decals are used for what's supposed to be scorch marks left behind by the lasers, missing sound effects, etc.
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