Prey

Give one signature tool so many jobs that players never put it away. Prey's Gloo cannon freezes enemies and lowers their defence, plugs gas leaks and flames, patches broken circuits, soaks up toxic spills and moves heavy objects Morgan can't lift through the physics system.

The freeze sets up combat rather than replacing it: it gives a window to swap to a stronger weapon, scan the enemy with the psychoscope for research, or run. The full name is the Gelifoam Lattice Organism Obstructor, and it sits alongside Kratos' Leviathan Axe and Mario's cap as a tool that "serves so many purposes that you'll always want to have it on quick-select."

Making Gloo climbable turned a handy gadget into essential equipment. Gloo sticks to almost any surface except glass and stays indefinitely, so players build their own staircases up to rooftops and upper floors.

Lead system designer Seth Shain says a space station with space outside means "everything has a ceiling," so the bounds were already set and the team could allow fluid movement. Arkane's Dishonored had to limit movement with high walls; Gloo climbing reads as a more intentional version of the Deus Ex trick of climbing on LAM mines.

Interlocking abilities let players invent solutions nobody scripted. The Lift Neuromod blasts heavy objects into the air, and players can Gloo them to walls as floating platforms.

Destroying the Gloo to drop an object on an enemy works in theory but is mostly luck: about 30 minutes of trying produced only a poor result.

Expressive traversal tools make sequence breaking likely, and Prey accepted it. Gloo lets players climb the Arboretum's locked grav shaft into Alex's office hours early, long before they have the key code or enough Neuromods to hack the lock, and it enables a full run in under 7 minutes.

The climb takes a lot of Gloo and patience, and Arkane probably didn't intend it. Gloo can also be used to clip through walls in speedruns.

A tool that serves every approach reinforces a game built on choice. Prey asks players to choose at every turn: human or alien, save or sacrifice, which Neuromods, who to trust, even their character's gender. Gloo supports combat, pacifism, exploration, problem solving and sequence breaking alike.

Quote: "it can serve you no matter how you choose to play."

Throw enemies at players the moment they get a new tool. Right after the player picks up the Gloo cannon, a Mimic invasion floods the area, and hitting them with blobs reveals the freeze effect with no tutorial text.

Put a visible reward next to a new ability, then demonstrate it again later. Beside where the player gets the cannon, a half-finished staircase leads to a roof with goodies, and a broken grav shaft elevator invites a Gloo staircase to the next floor, which holds extra items and early access to a new weapon.

For players who miss it, a character later builds a Gloo staircase in front of them to reach an escape route, repeating the lesson without forcing it on those who already figured it out.

Tools that add objects to the world need firm technical limits. Gloo blobs are solid, standable objects, so Prey caps blobs per area and stops Gloo from sticking to other Gloo, which rules out towers and bridges.

Seth Shain says chains of blobs added too much computation: "There was no way we could do this and have it perform on console." Adding objects strains frame rate, memory and collision, which is why other games constrain creation: Minecraft's voxel grid, Dreams' creation budget, Shadow Complex's 2D foam gun. Ammo usually runs out before the per-area cap.

Prototype until you hit the best mix of performance and fun. The Gloo gun went through many iterations and prototypes. Lead designer Ricardo Bare called the final version "the best intersection of: performs well enough to ship and is the most fun."

Bare said this to PCGamesN.

Prey turns enemy threats into player powers, then attaches a price. The Mimic can disguise itself as any object, even a health pack, and Neuromods let players take that power, such as becoming a coffee mug to roll through a door gap. Install too many and Talos I's friendly robots read your DNA as alien and attack.

Arkane solved late enemy variety with a cheap invisible enemy. Late in development Arkane needed more enemy variety but lacked time, artists and AI programmers, so it made the poltergeist, an invisible enemy that throws nearby physics objects and cost far less than other foes.

It became designer Ricardo Bare's favourite enemy. He says "good designers understand how to solve problems within the constraints that they have."