The developers explicitly set a goal that all game content would be accessible by spending only in-game currency, which is usually accomplished by those players who paid real money selling their unlock items for in-game currency via the trade/market/mall system. For instance, when visiting "That 70s Volcano" via a permanent pass, the paid player can collect "volcoino" tokens, trade some of them for a single-day ticket to the zone, and sell that in the mall for meat. The unpaid player buys the ticket with meat, uses it (consuming the item), and can visit "That 70s Volcano" for one day.
There are no timers. Every day, at a specific time, everyone gets a quantum of "adventures", which are kept if not spent, up to a cap of 200. Certain actions in the game can add additional adventures. You spend your adventures, at any time you please, and then you're done until the next day.
This system has been the best free-to-play game setup I have ever experienced. The devs actively try to avoid pay-to-win. It's mainly pay-for-convenience and pay-for-prestige/fashion. Everything you can buy for real-world cash can be bought for meat, and a lot of the items that were attainable for real-world cash in the past can still be bought for [more] meat. It intentionally avoids all three of the three trade-offs in the article.