Moom - Move your mouse over the green zoom button in any window, and Moom's mouse control overlay will appear (as seen in the above animation).
Godot Engine - Feature-packed 2D and 3D open source game engine.
Hammerspoon - This is a tool for powerful automation of OS X.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Spectacle App - Move and resize windows with ease.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.