"These source ports aim to reproduce behaviors of original executables for DOS, including bugs, at least if it's not too difficult (e.g., anything that greatly depends on the memory layout). With the exception of The Catacomb Armageddon/Apocalypse, this also includes compatibility with saved games for original DOS executables (done per version). The Chocolate Doom source port can be considered an inspiration for that. In fact, originally this codebase started as a Keen Dreams port titled 'Chocolate Keen Dreams'. With the addition of support for The Catacomb Abyss, and also in order to be a bit more original, the titles of 'Ref Keen Dreams' and 'Ref Catacomb Abyss' were coined. Similar titles were later used for the other Catacombs, with no specific name for the codebase. There are chances some of these names are still found, here and there. As of this release, the whole codebase has the title of 'Reflection Keen'."
ReflectionHLE (previously Reflection Keen, also known as Reflection Catacomb) is a source port for Keen Dreams, as well as Catacomb 3D, the Catacomb Adventure Series, Wolfenstein 3D, Spear of Destiny and Super 3D Noah's Ark created by NY00123. Although at first brush this seems odd, given the former is a 2D side scroller and the latter are 2.5D first person shooters, the games share very similar code bases outside of the rendering. This includes sharing the same tile map format called GameMaps for the TED editor, as well as the Paddle War mini-game based on Pong accessible from the main menu in both Keen Dreams and Catacomb 3D. The port can officially be built for Microsoft Windows, Linux and Android, but has also been tried on macOS and Amiga OS. The source port itself is fairly conservative, explicitly inspired by Chocolate Doom, other than adding more graphic options. One stand out feature is that it emulates the screen border flashes seen in the original game on old CRT monitors, most commonly when taking damage but also to indicate passable walls in Catacomb Apocalypse, so that they work on modern LCD screens. It also gives users the ability to not worry about regulating CPU cycle rate, as setting them too high in DOSBox can cause screen flickering.
"A lot of the original Keen Dreams code base, with changes, was re-used by id Software not only in the later Keen games from 1991 (i.e., Keen 4-6), but also in Catacomb 3-D. This should explain why do Keen 4-6 and Catacomb 3-D seem to share features like the control panel (menu), including the Paddle War game. While the later Catacomb games may have the control panel and other features removed or replaced, they're still clear derivatives of Catacomb 3-D. The Wolfenstein 3D sources are also based on Catacomb 3-D, and again share a lot of similarities."