Today I want to talk about two excellent games: XCOM 2 and Invisible, Inc. In the macro, they are very similar: both are turn-based squad-controlling strategy games. Both generate tension by giving the player seemingly impossible challenges. But the ways in which they use randomness to create drama and challenge differ dramatically.

In XCOM, the key to a healthy, happy workforce is optimizing your chances of a successful action. You do this through exploiting the terrain, gaining abilities and stats, and flanking the enemy or destroying their cover.

At the same time, you’re looking to reduce the enemy’s advantages over you, by using safe cover, not letting them flank you, and most importantly, killing them before they get a chance to shoot back. Nearly every action comes down to a dice roll, so the entire tactical portion of the game is about mitigating risk.

Invisible also has randomness deep in its DNA. Levels are generated procedurally, and with dramatically more variation in difficulty than XCOM 2’s levels. Rewards available in shops are randomized, giving you the choice of adapting to unfamiliar tools or hoping that the next level holds something better.

But Invisible is adamant about never making the outcome of your actions random, even at the expense of realism. If you can knock out a guard, he’ll be knocked out every time. Before you step into an unexplored hallway, you can see if your move will trigger an alert, even if you can’t yet see the camera itself. You can even spend an action to see where a guard will move next turn (with no explanation as to why you can either read minds or see the future.)

Yet with all this information, Invisible never feels like a puzzle game. It feels tense and dynamic, but that dynamism comes not from uncertain outcomes but from limited resources. Rarely can you do everything available in a level; as you hem and haw about which safe to crack and which hallway to explore, the alarm is ratcheting up and adding new, terrifying elements to the level. The longer you stay, the tougher things get, and the harder it is to get at the vital rewards you need to survive the final, grueling mission.

By making objectives optional and escape nearly trivial, most precarious situations you find yourself in are dooms of your own devising. If you don’t take enough risk, eventually you’ll fall behind the power curve and be overwhelmed. But because you chose to take the risk, it always feels fair when the plan falls apart and your rag-tag spy agency collapses on itself.

XCOM’s objectives are rarely optional. Even on time-sensitive missions, if a group of aliens is between you and the evac zone, it’s almost always preferable to kill them rather than flee. Rather than flexible goals and limited resources, XCOM uses randomized outcomes to create tension. And while it doesn’t feel “unfair” when a 29% chance to hit misses, it does feel unfair when moving several tiles to the right unveils a group of enemies previously obscured behind a tree. Having perfect information means when you mess something up, it really feels like your fault.

This also applies to the strategy layer in XCOM 2; while at first it seems overwhelming and complex, over time it becomes clear there is a simple hierarchy of things to invest in, and choice becomes trivial. The tension comes not from choice and risk, but from the randomized reward (“I hope I finish recovering this soldier before the next terror mission”.)

Invisible, Inc. walks an incredibly fine line by providing the player perfect information on the outcome of their actions, but still creating tense, risky challenges that feel dynamic and turn out in unexpected ways. XCOM avoids much of this difficulty by obscuring information from the player.

Despite these shortcomings, XCOM has generated more memorable, dynamic stories for me than Invisible. Part of that is certainly down to the sheer volume of stuff in XCOM 2, but there’s also an interesting game design lesson about how to create tension and memorable anecdotes: you can either create an intricate, delicately balanced system of rewards and limited resources, or you can throw a little randomness in. Just be careful to expose that randomness to the player, and give them meaningful ways to mitigate it.