A simple physics sandbox.

• ECS-like architecture achieved through multiple inheritace
• Sand, Water & Gas Physics
• Buoyancy
• Heath transfer
• Status changes (ice -> water -> vapor)
• Scriptable custom tile behaviours

• Click with the Left mouse button to add the selected Tile
• Click with the Right mouse button to delete the tile you are hovering on
• Use the Mouse wheel to select different tiles
• Press Space to Pause/Unpause the simulation
• Press F1 to enable additional information
• Press ESC to reset the world
• Press Left CTRL while adding or deleting tiles to enable big brush mode

For being pure python it's as good as it gets (without using multiprocessing or Cython), i would suggest using PyPy.