Pay Wall

The game becomes impossible to continue playing without payment.

A Pay Wall is a point in the game where you must pay money to continue playing the game. If the game makes this clear ahead of time, then this isn't a Dark Pattern. Perhaps the first 5 levels were a free trial to see if you like the game and then you can purchase the rest. This is essentially the "Shareware" model of game development which is not a dark pattern. A similar practice is Downloadable Content (DLC). With a DLC, you purchase additional content that extends the standard game that you already have. If the DLCs are known ahead of time, this is a clean practice.

It becomes a Dark Pattern when the game doesn't disclose this ahead of time and surprises you with this information after you have been playing for some time. If you have played part of the game already, it may have some endowed value for you, or you may have a partially completed goal that you want to finish. If the game suddenly stops working until you pay to unlock the complete game, you may have a strong incentive to pay. To avoid this dark pattern, games should be up-front about the cost and how much you can pay for free.

A game may also contain a secret hidden Pay Wall. This occurs when the entire game is free, but the difficulty increases steadily until it's nearly impossible to continue without purchasing in-game items or upgrades that make it possible overcome a particularly difficult level or obstacle. The game doesn't directly prompt players for payment, but instead relies on their growing frustration with being unable to beat a level to drive sales of in-app purchases of upgrades.


Examples

Rotaeno Rotaeno
"Some chapter of the game, even some new main ones are DLC"

Hearthstone Hearthstone
"One of the game modes require payment to enter - tickets can be earned in game though and the mode requiring payment is not the main one"

Idle Angels Idle Angels
"You cannot complete certain stages without enough power. The further stages you complete, the more competitive your account becomes."

Minecraft Minecraft
"Promoted multiplayer servers have paywalls."

Asphalt 9: Legends Asphalt 9: Legends
"Almost all in-game activities have previous content requirements, which greatly benefit only long time players."

Arcaea Arcaea
"If you want more songs"

Magic: The Gathering Arena Magic: The Gathering Arena
"Some events are heavily paywalled, where you can only use Gems and it's basically impossible to get multiple entries from converting gold to Gems from Drafts."

Shadow Fight Arena Shadow Fight Arena
"Incredibly hard to advance , there is a dojo level that masavly increase stats if you upgrade enough"

Phobies Phobies
"Eventually, you will reach a point where everyone else's 'fears' are level 10-13 while yours are at level 7-8. You either pay to get your units levelled up or grind for months to reach the same level as everyone else."

Clash Royale Clash Royale
"No way to advance as free to play"