Impromptu Games is Joe Wintergreen's game dev company, which is usually just him.

Sometimes available for work - enquire here. There's also a blog.

Technical Designer at Free Range Games on an unannounced title.
Briefly helped out Summerfall Studios with some technical art and console concerns on their roleplaying musical Stray Gods.
Worked VFX for Uppercut Games, creators of Epoch, Submerged and City of Brass, on an unannounced project. Use Niagara, Blueprint, and materials to make various cool secret things happen.Worked for a few years as a Systems Designer and Technical Designer on Weird West, an action/RPG from the creators of Dishonored and Prey. Designed or implemented very many of its systems, and later was brought back to create its First Person Mod
Contracted by Nightdive Studios to help out with optimisation on System Shock 1ís UE4 remake in advance of its appearance at GDC 2019. Afterwards, the demo was able to be presented at 60FPS in HD.Assisted Mischief with various optimisation, UI work, polish and dejanking on their cinematic first-person game Adios.

Also ported the game to the Nintendo Switch, where it runs at a solid 30FPS with minimal compromise to its aesthetic. Details.
Worked for several years on The Siege and the Sandfox, an upcoming 2D Stealthvania being built on UE4 by Cardboard Sword. Worked on various Blueprint systems, including building a custom AI plugin to allow the AI to be built and debugged more easily than with Unreal's behaviour tree system.Assisted Cardboard Sword with Transmission, a game where youíre an overnight courier in an open world of chilled-out synthwave vibes. Think Euro Truck Simulator meets Jalopy on a rainy summer night in 1986. Built road authoring tools and various other systems.
Assisted Modern Storyteller with NPC dialogue and conversation systems early in the development of The Forgotten City.
Primal Carnage Onslaught, by Pub Games, is the VR spin-off of the popular Primal Carnage FPS series. Pub contracted us to help with various polish such as effects, gun-feel and VR tutorial systems.
Contracted by Unity in 2016 to spend time with various level design tools and advise Unity on how best to improve its inbuilt level design support.Immersive Entertainment contracted us to assist with various aspects of their Grand Canyon VR Experience. Among other things, handled the implementation of motion-controlled rowing and the artificial intelligence systems (butterflies which alight on surfaces, feedable fish, etc).
InFlux Redux is an upcoming high-definition remaster of our 2013 puzzler InFlux, built on a brand new engine with improved graphics, physics and game code.InFlux (2013) is a puzzle game of exploration and puzzle platforming in a series of beautiful natural and abstract environments.
Stolen Steel VR (2017) is a room-scale VR arena swordfighting game. One-on-one physically-simulated sword combat against AI that blocks, dodges and parries.Vroom! (2011) was an iOS racing spin-off of the Source mod Shotgun Sunrise, made with Unreal Engine 3.
Shotgun Sunrise (2009) was a multiplayer zombie-Western total conversion mod for Half-Life 2.Impromptu Vector Field Painter is a tool that allows easy authoring and visualisation of 3D Vector Field assets, which are traditionally difficult to work with, in real-time, optionally in VR. The resulting vector fields can be saved out to .FGA format for use in other software or as game development assets.
Impromptu Ladders is a blueprint for UE4/5 which simplifies the task of creating ladders to fit spaces in your levels. A huge time saver for any game with ladders in it.Impromptu Handrails is a blueprint for UE4/5 which simplifies the task of creating handrails for your levels. A huge time saver for any game with handrails in it.
Impromptu Stairs is a blueprint for UE4/5 which lets you create detailed linear staircases in seconds out of instanced meshes, which is less annoying than other ways of making staircases. A huge time saver for any game with stairs in it.Impromptu Fire Propagation is a fire propagation system, similar to the one found in the Far Cry series, created entirely in Blueprint. Fire can spread realistically across meshes, landscape and other geometry.
Corkboard is a multiplayer post-it note/discussion system created in UE4 Blueprint. A good learning resource for anyone struggling with implementing basic replication tasks.MultipleCableActor is a simple free tool for UE4 that makes it easier to string up multiple connected CableComponents around your levels. Allows you to specify slack per-section and keeps texture tiling consistent across all cable sections.
Sir Isaac Fruiton is a game jam game created with Chris Murphy and Matt Peadon for the Epic MegaJam whose theme was "Standing on the Shoulders of Giants". It won the Allegorithmic Prize. In it, Sir Isaac Newton stands on the shoulders of up to four player-controlled Mecha-Newtons, snatching apples from trees to bring on scientific epiphanies. Joe Wintergreen's Deus Ex Lipsync Mod is a mod for the original Deus Ex which improves the game's broken lip syncing functionality, smoothing out the result and fixing a few bugs.
Hedy is an experiment in making better, more reactive headcrabs than Half-Life 2's using powered ragdolls. Half-Life: Alyx later did the exact same thing!

Documented the process here.
Last Round is a multiplayer FPS party game with semi-stealthy spytech vibes, which is being casually developed and may yet ship. Concept art, gameplay, twitter.
Magenta Sunset was a mysterious first-person road-trip adventure game which was cancelled, but resulted in a cool trailer.Spacething was a first-person game about renovating a friendly sentient spaceship, which was cancelled, but there's some cool prototype footage.