fixes:

- using 1 func for grid collision checking with func arguments in
  player and obstacle systems.
- moving obstacles now kill player if business ends points toward him
  on contact
- added retry in popup menu

components/velocity.go

@@ -61,6 +61,8 @@ func (velocity *Velocity) InvertDirection() int {
 		return South
 	case All:
 		return Stop
+	case Stop:
+		return Stop
 	}
 
 	// should not happen