light levels are roughtly implemented. the shader has to be
adjusted so they actually have an impact on the resulting color
+ there seems to be a bug with propagating light across chunk borders
+
+ also: how could block light affect entity lighting?
+
gravity
maybe like light levels? should also store a direction with it in
maybe divide into biomes and add special features like
settlements, ruins, all kinds of interesting stuff
+
+entity/world collision
+
+ entities should be stopped from entering solid parts of the world