Loops are an entirely different way of playing with the Block Party cubes! They weren't even discovered until about a week after Block Party's invention, and their play styles have evolved and matured much since then. The core mechanic surrounding loops is the notion of a 'neighbor' icon. Two icons are neighbors if they are only one step away from each other, for example
since they are only different in one way. A 3-loop is an arrangement of three blocks (see the picture) such that all touching corners are neighbors. Similarly a 4-loop is four blocks with a square in the middle, and so on for 5-loops up to 8-loops. Finally, a 2-loop is two blocks put together sharing an edge such that the icons across from each other are neighbors.
Loops can be used in a classic party setting (see the variations at classic party) where players attempt to form loops in their head and call "Party!" to form them, afterwards rolling the blocks used. This can be modified to suit players of many skill levels where a player who is averaging a higher number of loops gets assigned a higher loop count. For example, if they are making 2-loops very quickly other players can ask them to start instead making 3-loops (and so on--no players I know of can make 6-loops as quickly as complete beginners can make 2-loops, much less 8-loops!).
This allows players of many skill levels to play at the same table amicably and even keep score, while also encouraging all players to continue improving themselves rather than complacently sitting in mastery of something too easy for them.