Apparatus is a mobile game all about creating interesting contraptions and intriguing challenges. The Apparatus mode allows you to build all sorts of mechanical contraptions and then control them using the Control Panel object. The Challenge mode allows you to construct puzzles for the player to solve, making a blue marble get into the blue basket.
Apparatus was developed by Bithack AB during 2011 and is the predecessor to Principia. Unfortunately the game does not exist in any official capacity anymore, being taken down alongside Principia. It is however still loved by a small but passionate community that still keeps the game alive after all these years, including creating this site.
Apparatus-web is an open source unofficial reimplementation of the official Apparatus community site, created by the community for the community. It is forked off of principia-web's codebase with changes to better suit Apparatus.
The GitHub repository of apparatus-web can be found here.