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A falling sand game is a term given to a subgenre of games known as particle simulation games. They allow the user to place particles of different elements on a "canvas". The particles can interact with other particles in various ways, and may be affected by gravity, in some games. Many complex effects may be achieved. Many versions of the Falling Sand Game have been written since its introduction in 2005.
The original game first appeared as a web-based Java applet on the Dofi-Blog (Japan) in 2005. Since then, many variations of the game have appeared, most notably Burning Sand and wxSand, which introduced user-created element sets, known as mods.
Falling sand games are generally browser-based, using Flash or Java. Examples include:
- World of Sand (2005, Java)
- wxSand (2006, Windows)
- This is Sand (2008, Flash)
- The Powder Toy (2010, C++)
- The Sandbox (2010, Flash)
- ReactionLab 2 (2015, Android)
There is also a Steam/OS X/iOS/Android/Blackberry version of The Sandbox available through its homepage. 
Although the various sand games have differences, they share many similar characteristics:
wxSand, The Sandbox and The Powder Toy are the only downloadable game with a Macintosh version, other than the Java-based EnigmaSand. They may be able to be run in GNU/Linux using WINE. The browser games may be played on any computer with Java installed. The Sandbox has versions in Android, iOS, OS X, Steam (OS X & Windows) and Blackberry. ReactionLab 2 is currently exclusive to Android.
All games have adjustable pen sizes. Some allow the user to select different pen shapes. The pen is generally controlled using the mouse (Etch-a-sketch Sand is an exception).
Many falling sand games include multiple elements that are heavier or lighter than each other and can interact. For example, BHOL is a virtual black hole in The Powder Toy. By applying positive gravity, it attracts other elements and consumes them. Another example would be lava in The Sandbox, which, after cooling, becomes stone.
Downloadable games also have the ability to save "sandboxes", or images that can be uploaded to image hosting websites and later downloaded and played in the game. PNG and GIF format are usually used; JPG is not due to its poor compression.
- The Sandbox has a crossplatform online gallery where people can share their creations.
- The Powder Toy has online 'saves' where people can view the creations of others, and usually play with them.
More commonly found in stand-alone downloadable games, mods or plugins can be created by making use of scripting or by editing configuration files that control the various types of particles, their physical properties and interaction rules.
Most sand games use very simple physics: particles either fall, rise, or are fixed, and may drift from side to side. The Powder Game and The Powder Toy are two of the few games with more realistic physics, including wind and pressure. The Powder Toy also includes heat and ambiental heat, newtonian gravity, and water equalisation. The Sandbox includes dynamic lighting, weather, temperature with room temperature support and multi particle elements.
Humans (Or Human-Like Figures)
Some Falling Sand games have elements that are meant to represent humans, or to create a likeness to them.
- The Sandbox uses elements literally called humans, which after placement you can then decide their roles in a society that you create.
- The Powder Toy uses an element that has a fixed position as a 'spawn point' for its human element, called STKM (stickman). This acts as the permanent start place for the stickman, and is indestructible.
Multi Particle Elements
The Sandbox has dozens of elements that are made of more than one particle. It even has controllable vehicles and AI controlled characters.
- Carless, Simon (2005-12-24). "Welcome to the World of Sand". GameSetWatch. Retrieved 2011-06-21.
- Quilty-Harper, Conrad (2006-02-15). "Falling Sand: The Sequel". Joystiq. Retrieved 2011-06-21.
- Lowensohn, Josh (2008-07-07). "'This is sand' offers sweet reprieve for landlocked office drones". cnet. Retrieved 2011-06-21.
- Simon (2010-06-24). "The Powder Toy". Powder Toy. Retrieved 2011-10-01.
- onimatrix (2010-12-28). "The Sandbox on Kongregate". The Sandbox. Retrieved 2011-11-01.
- HF Games (2014-07-18). "ReactionLab 2 Homepage". ReactionLab 2. Retrieved 2014-08-20.
- onimatrix (2013-10-25). "The Sandbox Homepage". The Sandbox. Retrieved 2013-10-25.
- Powder Toy Lua API
- WxSand Modding Guide