A fun online physics puzzle game!

Apparatus is a sandbox puzzle game for Android devices. Use your hammer to pin planks and wheels together to build anything you can imagine, connect your apparatus to motors and give them power using batteries.

Admittedly, I haven't tried it, but it looks like a lot of fun and I really like sandbox games. I almost wish I had an Android device now.

This tool lets you programatically (or manually) simulate keyboard input and mouse activity, move and resize windows, etc. It does this using X11's XTEST extension and other Xlib functions.

Additionally, you can move, resize, hide, and modify window properties like the title. If your window manager supports it, you can use xdotool to switch desktops, move windows between desktops, and change the number of desktops.

The optical appearance of the stellar sky for an observer in the vicinity of a black hole is dominated by bending of light, frequency shift, and magnification caused by gravitational lensing and aberration. Due to the finite apperture of an observer's eye or a telescope, Fraunhofer diffraction has to be taken into account. Using todays high performance graphics hardware, we have developed a Qt application which enables the user to interactively explore the stellar sky in the vicinity of a Schwarzschild black hole. For that, we determine what an observer, who can either move quasistatically around the black hole or follow a timelike radial geodesic, would actually see.

OpenTTD is an open source clone of the Microprose game "Transport Tycoon Deluxe", a popular game originally written by Chris Sawyer. It attempts to mimic the original game as closely as possible while extending it with new features.

FlightGear is an open-source flight simulator.