Add main.go in cmd/square
Add SetUpRect in cmd/square
Add PickyForce in cmd/square
Add ParticleRect in cmd/square
Add ParticleRect.Size in cmd/square
Position particles in cmd/square
Document ParticleRect.Size
Fix ParticleRect.RowAndColumn
Add ZeroForce to cmd/square
Add Formatter to cmd/square
Let a Formatter remember where to write to
Run a simulation
Add TestRowAndColumn to cmd/square
Fix ParticleRect.RestingPosition in cmd/square
Document ParticleRect.Run in cmd/square
Add Hooke's force into the simulation
Change vect.Vector.Unit's treatment of 0