Sandboxels

Overview

Drop a single pixel of sand onto a single pixel of water and the sand sinks while the water rises, and the entire premise of the sandbox is implied in that one exchange. Sandboxels is an in-browser falling-sand simulator written in pure JavaScript on an HTML5 canvas and maintained by the R74nCom project alongside a large open-source contributor community. The canvas hosts over five hundred elements and thousands of reactions governed by density, temperature, charge, and chemistry: fire climbs wood and exhales smoke, lava poured into water quenches into stone, acid dissolves metal, and electricity arcs along wires to ignite explosives. There are no levels, no win state, and no objective beyond the experiments you stage — a column of sand suspended over a pool, a live circuit, a slow chemical burn — which places it next to powder-toy style sandboxes for tinkerers, educators, and the merely curious.

How to Play

All input runs through the mouse. Left-click and drag to paint the currently selected element onto the canvas, right-click to erase, and middle-click to eyedropper whatever element sits under the cursor. Scroll the wheel, or press the Plus and Minus keys, to resize the brush, and hold Shift while clicking to draw a straight line. Pick elements from the category bar along the bottom, press E to search a material by name, and step between categories with the Left and Right arrows. Hit Space or P to pause the simulation while you set up a scene, then unpause and let the reactions resolve — a typical session is selecting sand, pouring a column, switching to water, flooding the base, and watching what sinks, floats, or ignites.

Tips & Strategy

Pause before you build. Freezing the simulation with Space lets you stack a sand column over a water basin, lay a gunpowder fuse, or wire a battery to a switch before anything reacts, then a single unpause fires the whole chain at once. Exploit density: heavier liquids sink beneath lighter ones, so oil floated on water and ignited from below sweeps flame across the surface, and sand dropped into water displaces it upward, the cleanest way to build layered terrain. Learn the category order along the bottom bar, because the Left and Right arrows jump you between groups and knowing where fire, metal, and powder sit saves constant scrolling. If a reaction runs away — fire you cannot smother, acid eating the canvas — lower the TPS readout in the top bar to slow time and diagnose it rather than hitting Reset, and use middle-click to sample any element you cannot name.