Since the theme was "Energy equals Matter", I decided that energy would produce 'matter'. But what is matter?
mat·ter
noun
- 1. physical substance in general, as distinct from mind and spirit; (in physics) that which occupies space and possesses rest mass, especially as distinct from energy.
From that definition, matter is basically anything that is tangible. Grass is matter, shoes are matter. If you touch it, it is matter. This whole game is about trading energy for tangible items.