Puzzle can be used for Entertainment. Entertainment is related to Play. 
Real is a synonym of Substantial. Substantial is a synonym of Strong. Strong is related to Stretch. Stretch is related to Mark. 
Puzzle --UsedFor--> Entertainment <--RelatedTo--> Play 
Real <--Synonym--> Substantial <--Synonym--> Strong <--RelatedTo--> Stretch <--RelatedTo--> Mark 