There are 10 seconds left in the match. My opponent and I each have one tower left. Mine has a little over 100 hit-points, and there’s a swarm of little skeletons coming my way. My opponent’s base has 200 hit-points. There’s no way to get any of my units there in time. I deploy a unit to reveal my next card. Drawing “fireball,” I quickly throw the projectile at the opposing tower. With mere seconds to spare, the tower goes down right before my opponent topples mine. For my struggle, I get a couple more trophies. But I don’t mind. It was a good use of three minutes of my time.

This is the rhythm of Clash Royale, a real-time strategy-tower defense hybrid mobile game for Android and iOS devices and developed by mobile app giant Supercell.

The game mechanics are deceptively complex. The player gets cards by opening chests, winning battles or spending currency in the shop. Then, the user builds a deck of eight cards ranging from large, strong units meant to push towers down to small mob units that can counter the former. This gives the game a smooth ebb and flow. There’s always a counter to any unit, meaning that any strategy relies on patience and forethought. Maybe you know your tower can weather the assault of one unit, so you send a horde of ranged attackers to push up the opposite lane. Or, if you’re worried, you place this unit on top of the attacker and watch as your tower remains untouched, unless the enemy has a rain of arrows to take out your low health units. You can then take the opportunity to send more across the bridge knowing your opponent has no defenses. There’s a lot of thought that goes into playing this game.

With more wins, the player advances through different arenas, gaining access to new cards. However, many of the game’s top players use cards from the first arena in their decks. In this way, the game is somewhat balanced. At times, you might feel as if your efforts are hopeless, that a certain card used against you is clearly broken. But then there’s that moment of clarity, the realization that there is something you can do. It’s these small moments of insight that improve your skill.

There is a point, however, at which some cards become more powerful than others. When the player collects multiple copies of the same card, gold can be spent to level that card up, giving it more health and attack power. A level 3 card will always beat the same level 2 card. This would be fine if everyone got cards at the same rate, but the game’s sinister business practices undermine much of its potential balance.

You can buy large card chests with gems, a type of in-game currency gained by leveling up. The rarest of these chests contain the best cards in great quantities, which means you can level your best cards at a faster rate. If you don’t have enough gems, real-world cash can be spent at the in-game store to get more, allowing you to buy more chests and, thus, have more of the best cards. In this way, the monstrous influence of the “pay-to-win” strategy emerges. Supercell also developed Clash of Clans, another highly successful mobile free-to-play game with intrusive micro-transactions. The free veneer of these games is meant as bait to make money once players get hooked. Most of the time, the top players are also the players that spend hundreds of dollars on shop items.

Regardless, I haven’t spent any real money in the game, and I don’t think I ever will. I’ll most likely hit a ceiling, at which point I won’t be able to progress, but I’m fine with that. I’ve gained a substantial amount of pleasure from my time already, and while the game’s financial practices have been decried by many, they’re fine with me. I’m just going to keep on playing, free of charge.