The Powder Toy is a free 2D physics based sandbox game, which lets you manipulate a variety of elements based on their chemical/physical properties. Inspired basically from a variety of Java based games such as the "Falling Sand" game and the "Powder Game", the Powder Toy brings you a similar but more complicated experience to your desktop.
At first, it might not look like much. But once you get to explore all its features you will probably notice it can get pretty complex. From creating simple concrete walls and test different materials on them (Such as pouring Lava on them or blowing them up with C4), to creating functional circuits or even more complex combinations which include electricity, radioactive materials, elements with more advanced properties (Unstable molecular structure or rapid expansion/retraction of their volume), the variety of the things you can do are literally infinite.
The game features a simple basic looking interface which easily lets you navigate through the different elements and also features many options regarding the actual simulation of the physics on screen (Ambient Heat, Newtonian gravity e.t.c) as well as different display options. Graphically it looks simple, but it can become quite impressive as fire/smoke effects look and mostly behave quite realistically. The game also simulates pressure and temperature effects. (It is worth pointing out that when many reactions take place on screen, older PCs may experience noticeable slowdowns.)
In addition to that, the game is constantly updated with new versions featuring from bug fixes to new elements or display modes and options. Once you have created something you can also upload it to the ingame online library and share it with other users. (You can as well download other user works).
To summarize, despite its simple looks and small size, The Powder Game is an innovative game with one of its kind features that can become a really addictive way of killing some time, if you like physics based sandbox games.
You can download it from here: