Free-to-Pay 

A game that is free to play yet cuts the player off at key moments to demand payment. This can occur after losing too many lives, completing a chapter, or forcing the player to make a purchase in order to fulfill an objective necessary to complete a larger objective.

"Battle Nations is an addictive and hilarious turn-based strategy game that combines FarmVille with tanks! The game can be downloaded free, but players are free-to-pay for powerful, exclusive units and also to speed up construction time! Buy 1250 Nanopods for 49.99 USD, and get the edge on everyone else!"

Free-to-Pay by RedRockRun October 18, 2013

Free to Pay 

A category of common games with a common, plentiful currency, and a premium currency (commonly gems like diamonds, emeralds, and amethysts) that requires payment to obtain, and of which a handful is given to the player during the tutorial. More than often this "currency" is used to speed up an activity, or to acquire a premium object, usually far better than it's normal money counterpart. Common examples include, clash of clans, dragon city, roblox, trainstation, mobile strike, tuber simulator, etc

Jumbo John Do you play Roblox? It's the coolest game!
Billy McBobbo: Eh, I really try to steer away from free to pay games, ill pretty much have to pay to enjoy it

Free to Pay by BillBobbo69 October 31, 2016