Modern Half-Life 1 SDK for Xash3D FWGS engine, has enhanced graphics and physics and a lot of new features for mod-makers. Crossplatform, supports Windows/Linux. Based on XashXT and Spirit Of Half-Life.
I can't assume this implementation as fully completed. This should be merged as it is, so I'll be able to switch to other necessary tasks. But there are some things that should be done later in future (even maybe somebody will help with it):
Interpolating rigid bodies state when applying it for entities (because physics ticks with other rate than actual game loop)
Testing and fixing problems with dynamic actors and pusher entities interacting
Fine-tuning all minor physics-related things so physics can look more completed and playable
Vehicles (we even have some snippets derived from XashXT, hidden under macro HAS_PHYSIC_VEHICLE)
Ragdolls (for this we need some mechanism to transfer bone matrices data to clients)
Physical units (since engine uses inches instead of meters, we can't use common SI units and instead forced to use other weird units based on inch)
Made water actors movable, because func_water can be moved around map (now there is assumption that water is always static)
I can't assume this implementation as fully completed. This should be merged as it is, so I'll be able to switch to other necessary tasks. But there are some things that should be done later in future (even maybe somebody will help with it):