Optical Rendering
  The whole world is realistic due to real-time reflections and refractions!
Chemicals & Reactions
  The whole periodic table of elements and their compounds are free to use (as exhaustive as possible), with all kinds of reactions and all kinds of effects:
  Combustion, solution, precipitation...
Thermodynamics
  Matters can change state according to temperature: ice, water, vapor...
  Heat can transfer: different matters have different properties.