Game UI is different from app UI in ways that most product designers underestimate. Here's what I've learned.

**Rule 1: The context of play changes everything**

Users of your payment app are stationary, patient, and focused. Players of your mobile game are in a bus, one-handed, 20% battery, in a hurry. Every interaction needs to be thumb-friendly, interruptible, and forgiving.

**Rule 2: The third dimension is always present**

Even on a 2D phone screen, game UI exists in a spatial world. Your HUD needs to sit comfortably on top of dynamic, moving, sometimes chaotic game content. High contrast, proper layering, and appropriate blur are essential tools.

**Rule 3: Information hierarchy in games is inverted**

In apps, primary actions are large and obvious. In games, primary game view is most important — UI should be as small as possible while remaining usable. The best game UI is invisible until needed.

**Rule 4: Animation is not decoration**

In apps, animations should be subtle and brief. In games, animations communicate state — health dropping, resources increasing, a reward arriving. Game UI animations need to be noticeable and satisfying.

**Rule 5: The tutorial is part of the design**

The best tutorial is no tutorial — the game teaches itself. When that's impossible, design tutorials that are contextual, brief, and skippable. Nobody reads tutorial screens.

**Rule 6: Monetisation is a design challenge**

Every game designer eventually faces the in-app purchase screen. The ethical designer's job is to make monetisation clear, fair, and not manipulative. This is increasingly regulated and increasingly scrutinised.

**Rule 7: Test on real devices, always**

A game UI that looks great on your Macbook mockup often falls apart on a budget Android device with a small screen and a cracked display protector. Test on the devices your actual players use.