"Serious Engine", it is designed to cope with extremely large view distances and massive numbers of models by implementing level of detail rendering. Most contemporary FPS engines were developed for a limited draw distance and only a few animating models (i.e. enemies) on screen at a time. The Serious Engine is very efficient, capable of maintaining dozens of moving enemies (often stampedes) and enormous enemies, even on a modest system challenging the well known id Tech, Unreal Engine or Source engines. The "Serious Engine" can render through both Direct3D or OpenGL and, while it does not support pixel or vertex shaders, it is optimized for Direct3D 7's hardware transformation, clipping and lighting. The "Serious Engine" is available for licensing from Croteam. A more powerful iteration of the "Serious Engine" was developed for use in Serious Sam 2 and is known as "Serious Engine 2". It supports many features of modern GPUs such as pixel and vertex shaders, HDR, bloom, and parallax mapping. Serious Engine 3 was used in Serious Sam HD: The First Encounter and Serious Sam HD: The Second Encounter. It includes detailed shading, and enemies are completely remodeled to look more realistic. This engine is also being developed to harness the full capacity of HDR and High Definition mapping. An updated version, Serious Engine 3.5, is used in Serious Sam 3: BFE. The latest version is the Serious Engine 4, which Croteam used in their most recent game, The Talos Principle. In March 2016, Croteam released Serious Engine v1.10 as free and open source software on GitHub under the GNU GPL-2-0-only. Xbox version On 12 November 2002, both The First Encounter and The Second Encounter were combined into one game and ported to the Xbox titled Serious Sam. The game had notable differences from the PC counterparts, including the model of Sam being changed from the model of The First Encounter to a more cartoon style Sam, removing the shades to make him look less like Duke Nukem and more like he does today. The Xbox version includes all of the levels from both PC games, though some were modified due to the memory constraints of the Xbox console. As a result, the levels were made smaller by removing the areas outside of the playing area, and some larger levels were split into two smaller ones. Unlike the PC versions where the player can walk almost infinitely away