The Two Types of Randomness in Game Design

Video games are full of randomness: procedurally generated levels, random encounters, unlucky misses, card draws, dice rolls, roulette wheels, loot tables, and random number generators.

All of these systems involve outcomes that are not fully determined by the designer or the player. Something unpredictable enters the game and changes what happens next.

That unpredictability can produce wonderful moments, but it can also create unfair outcomes and frustrating failures. The same design tool can feel magical in one game and maddening in another.

One common use is variety. A strong generation algorithm can produce levels, worlds, characters, enemy combinations, and problems at a scale that handcrafting could never match.

Procedural content is rarely as carefully shaped as a fully authored level, but it offers diversity and volume. Shadow of Mordor's orc captains, Minecraft's enormous worlds, No Man's Sky's shared universe, and roguelike layouts all depend on randomness in different ways.

When a game generates a new layout every run, players cannot simply memorize the same stage over and over. They have to learn the underlying mechanics well enough to handle whatever the system creates.

Randomness can also balance a multiplayer game by reducing the absolute importance of skill. Lucky rolls and unlucky draws give less experienced players a chance to stay involved.

That is especially useful when the randomness favors players who are behind. Mario Kart's item boxes are more generous to racers near the back of the pack than to the player in first place.

This works best in party games, family games, and social games where mixed skill levels are expected. In competitive games built around mastery, too much luck can obscure who actually played better.

Randomness can make rewards more exciting. A rare weapon drop in a looter shooter feels different because the player knows it was unlikely. The low probability creates anticipation, surprise, and a stronger emotional spike when the result arrives.

That same mechanism can become manipulative. Random rewards can be tuned into a Skinner-box loop that extracts time, money, or attention rather than supporting the game.

The design question is whether the random reward makes the game richer or whether it mainly exploits the player's desire to roll again.

Randomness also shapes planning. A plan requires information: enemy positions, health values, available resources, and maybe even what opponents intend to do next.

More information can make plans stronger, but too much information can create problems. If every variable is visible, players may calculate far into the future, searching for an optimal move until the game slows into analysis paralysis.

Into the Breach shows the tension clearly. The player can see the board and every enemy attack for the upcoming turn, which makes the game deeply strategic. It can also make a single turn take a long time because every consequence is visible.

Perfect information can also make plans too stable. In Plants vs. Zombies, seeing the exact upcoming monster roster makes it easier to build a reliable defense. The result can become flat unless the game adds fresh disruption.

A useful concept here is the information horizon: the distance between the current moment and the point where information becomes known to the player.

Designers can limit that horizon in several ways. Chess does it through exponential complexity. Action games do it through execution uncertainty, because the player may fail to perform the plan. Strategy games use hidden information, such as fog of war.

Randomness is another way to limit the horizon. If certain future factors are unpredictable by design, players cannot make perfect plans. They have to prepare, adapt, and recover.

The most useful split is between input randomness and output randomness. Input randomness happens before the player makes a decision.

A roguelike level is generated, and then the player navigates it. A deckbuilder deals a hand of cards, and then the player decides how to spend them. Dicey Dungeons rolls dice, and then the player chooses where each die should go.

This kind of luck gives the player a situation to solve. The randomness creates the problem, but the player's decision still determines the response.

Output randomness happens after the player makes a decision. The player commits to an action, then luck determines the result.

The classic example is XCOM hit chance. The player orders a soldier to shoot an alien, but the game decides whether the shot hits or misses. Hidden enemy choices after pressing end turn, random encounters, and loot boxes all fit the same broad pattern.

This kind of luck is more likely to create anger because it can break a plan after the player has already committed. Failure may feel less like strategic error and more like the game taking control away.

That is why input randomness is often seen as friendlier to strategy. It asks the player to adapt around a random setup. Output randomness can undercut the strategy after the fact.

Some design histories show developers moving from output to input. FTL contains a lot of swingy output randomness, while Into the Breach almost completely exposes enemy intentions before the player acts. Slay the Spire became more fun when enemy plans were shown at the start of the player's turn rather than hidden until after it ended.

Still, this is not as simple as input good, output bad. Both are tools. Poorly controlled input randomness can damage a game, and carefully tuned output randomness can improve one.

Input randomness can make starting conditions so uneven that success becomes hard to judge. In Spelunky, an early shotgun or jetpack can radically improve a run. That creates exciting spikes, but it can also make unlucky runs feel less meaningful.

Some players respond by restarting repeatedly until the opening roll looks good. That can be an understandable behavior, but it means the random setup is encouraging players not to play the game they were given.

Slay the Spire addresses this by offering starting bonuses only if the player reached the first boss on the previous run. That rule encourages players to engage with imperfect runs instead of immediately rerolling for the best opening.

Many games limit randomness without removing it. Pandemic's setup shuffles epidemic cards into separate piles before stacking the deck. The process is a little fussy, but it prevents all epidemics from appearing at the start or all of them arriving after the game is basically solved.

Diablo 3's smart loot makes item drops more likely to match the player's current class, reducing pointless rewards. Modern Tetris uses a bag system that shuffles all seven pieces, deals them out, then shuffles a new bag, guaranteeing variety while still keeping the order unpredictable.

These systems do not eliminate luck. They shape it so the dramatic surprises remain while the most game-breaking sequences become less likely.

Another question is how often new random information appears. If a new random event happens at the start of every single turn, the information horizon can become so close that long-term planning disappears.

Good information flow often arrives in spikes. XCOM lets the player make a plan for a few turns, then disrupts that plan when a new enemy pod is revealed or reinforcements arrive.

That rhythm matters. A slow trickle of known information lets the player act with purpose. Occasional high-impact spikes force them to stop, regroup, and rethink.

Output randomness is not useless. In abstract combat systems, it can simulate mistakes, imprecision, and uncertain execution. If units never missed, many tactics games would feel strangely mechanical.

It also tests risk management. Good XCOM play is not only choosing a high-percentage shot. It is having a backup plan if that shot misses.

In that sense, output randomness can become input randomness for the next turn. The player has to deal with the consequences of the roll and form a new plan from the changed state.

One way to soften output randomness is to avoid all-or-nothing results. Phoenix Point simulates individual bullets through a ballistic system, so some bullets may hit and some may miss. That can feel less punishing than a single complete whiff.

Showing the odds is also important. If players know the chance of success, they can decide what risks are acceptable and understand how actions like moving closer change the calculation.

The complication is that humans are bad at probability. Players often read a 90 percent chance as a near-guarantee and a 33 percent chance as something that should succeed every third attempt. Many games quietly adjust the math so displayed odds better match player expectations.

Another way to make randomness easier to understand is to use familiar physical systems. A six-sided die is less abstract than a hidden computer calculation. Cards are also familiar, and they have a different kind of probability because drawing one card changes the makeup of the deck.

Dice-based games such as Tharsis and card-driven games such as Slay the Spire benefit from that familiarity. The player can reason about the random system because it resembles something they already understand.

Cards also support dependent probability. Once a card leaves the deck, future draws change. That helps create the cascading synergies and long-term deck reasoning that make many card games satisfying.

One especially safe use of output randomness is letting it surprise the player in their favor. Into the Breach includes a small building defense chance that can sometimes prevent damage when an enemy attack would otherwise land.

Players do not rely on it, so it does not become the foundation of a plan. But when it triggers, it feels wonderful because the expected bad outcome unexpectedly becomes good.

That distinction is important. Randomness that rescues the player from a disaster usually feels generous. Randomness that creates the disaster can feel hostile.

Randomness can provide variety, balance skill gaps, make rewards exciting, limit perfect information, create surprise, and turn players into risk-calculating tacticians.

It can also damage fairness, blur responsibility, encourage rerolling, manipulate reward psychology, and make failures feel arbitrary.

Input and output randomness are the most important distinction, but neither type is automatically right or wrong. The real design work is deciding when luck happens, how much it can swing the game, how visible it is, and whether the player gets a meaningful decision before or after it appears.