Welcome to The Simple Cube! In the modern age of Magic, card design has become more and more supplemented by the use of external game pieces namely tokens, counters, and double faced cards. Though these elements are all important in adding longevity and variety to the card designs, the combination of everything can be tiring. Hence, The Simple Cube's restrictions:
In addition to hard rules about cards mechanical capabilities I have a set of design goals mostly pertaining to what I would call the cube's "Mechanical Aesthetic":