About SandTrace
SandTrace is an offline particle simulation app that transforms your device into a mesmerizing physics sandbox. Draw with your fingertip and watch as thousands of tiny particles flow, collide, and interact according to realistic physical rules. Whether you are curious about how sand cascades, water flows, or fire spreads, SandTrace lets you explore these phenomena in an intuitive, hands-on way — all without requiring an internet connection or collecting any personal data.
Born from a fascination with emergent behavior and natural systems, SandTrace captures the beauty of particle physics in a format that anyone can enjoy. It is part creative tool, part science experiment, and entirely captivating.
Key Features
Multiple Particle Types SandTrace offers a rich selection of particle types, each with unique physical properties and behaviors. Sand particles pile up and cascade realistically, forming dunes and slopes. Water flows downhill, fills containers, and applies pressure to surrounding elements. Fire rises, ignites flammable materials, and produces smoke. Additional particle types include stone, oil, wood, acid, and more. Each element interacts with others according to carefully crafted rules, creating an endlessly fascinating web of cause and effect.
Draw and Interact Creating your simulation is as simple as touching the screen. Select a particle type and draw directly onto the canvas. Build walls of stone, pour streams of water, ignite piles of wood, or drop sand from great heights. You can adjust the brush size to place particles with precision or paint broad strokes across the canvas. The real-time response is immediate — particles begin moving and interacting the instant they appear.
Realistic Physics Simulation At the heart of SandTrace lies a sophisticated cellular automaton engine that simulates particle interactions at a granular level. Each particle evaluates its neighbors every frame, following rules that govern gravity, density, temperature, and chemical reactions. Sand settles into stable configurations. Water seeks its own level. Fire consumes fuel and extinguishes without it. The result is a simulation that feels organic and believable, even though the underlying system is elegantly simple.
Save Screenshots and Videos Proud of a creation? SandTrace allows you to capture screenshots and record videos of your simulations directly to your device’s gallery. Share your physics experiments with friends, post them on social media, or simply keep a personal archive of your most impressive builds. The capture functionality is built directly into the app — no external tools needed.
Completely Offline SandTrace works entirely offline. There is no need for a Wi-Fi connection or cellular data. The simulation runs locally on your device, which means you can enjoy it on airplanes, in remote areas, or anywhere else without connectivity. This offline-first design also means there is zero latency — every interaction is processed instantly on your hardware.
No Data Collection Privacy is a core principle of SandTrace. The app does not collect, transmit, or store any personal data whatsoever. There are no analytics trackers, no advertising identifiers, and no cloud accounts. Your creations exist only on your device unless you choose to export them. This makes SandTrace one of the most privacy-respecting apps available in the simulation category.
How to Play
Launch SandTrace and you are immediately presented with a blank canvas. Select a particle type from the palette at the bottom of the screen. Touch the canvas to begin drawing. Particles will instantly come to life, flowing and interacting according to their physical properties.
Experiment freely — there are no objectives, no scores, and no time limits. SandTrace is a pure sandbox. Build an elaborate structure from stone, then flood it with water. Create a chain reaction by placing fire near oil. Stack different materials to observe how they settle and shift. The possibilities are limited only by your imagination.
Use the eraser tool to remove particles or clear the entire canvas to start fresh. Adjust the simulation speed if you want to observe interactions in slow motion or fast-forward through longer experiments.
Target Audience
SandTrace appeals to a remarkably broad audience. Students and educators use it as an interactive demonstration of physical principles — gravity, fluid dynamics, and thermodynamics become tangible and visual. Artists and creative individuals find it a unique medium for digital expression, producing patterns and compositions that could not exist in traditional media. Children are captivated by the immediate, tactile responsiveness of the particles, while adults find it a relaxing, meditative experience.
The app is particularly well-suited for anyone who enjoys creative sandbox experiences, physics simulations, or simply watching beautiful patterns emerge from simple rules. Its completely offline, data-free nature makes it ideal for parents looking for a safe digital activity for their children.
Technology
SandTrace is built with Flutter and features a custom rendering engine optimized for real-time particle simulation. The engine processes thousands of particle interactions per frame while maintaining smooth performance across a wide range of devices. By leveraging Flutter’s Skia-based rendering pipeline, SandTrace achieves consistent, high-fidelity visuals on both iOS and Android.
The simulation engine uses a grid-based cellular automaton architecture. Each cell in the grid can hold a single particle, and every frame the engine evaluates each occupied cell against its neighbors to determine movement, state changes, and interactions. This approach balances computational efficiency with simulation fidelity, delivering a responsive experience even on older hardware.
Get Started
Download SandTrace today on the App Store and start exploring the fascinating world of particle physics. It is free, offline, and completely private — a sandbox with no strings attached.
Developed by Steven Huang at Atlantis Kid.