How to prototype a game: test the core loop before content production

What is the core loop, and what are you testing?

Describe the core loop in a few lines: what the player does, how the game responds, how they progress and why they want to do it again. If you cannot write this down simply, the prototype will struggle to answer anything clearly. A clear core loop is the starting point of any game development project.

Then choose the one uncertainty the prototype should resolve. It might be whether the controls feel clear, whether the level of challenge is right, whether the pacing holds attention or whether a specific interaction is enjoyable at all. One clear question tells you far more than a vague hope that the game “will feel good”.

Keep the playable scope small enough to watch people play it several times. Production art, a large story world and many levels make a prototype more expensive without helping you answer whether the central interaction works. Grey boxes and placeholder sounds are perfectly acceptable at this stage.

It also helps to decide early what the prototype is not. It is not a vertical slice, a pitch trailer or a technical demo of the engine. Each of those has its place, but mixing them into the first prototype blurs the question and slows down every iteration.

How should you watch people play?

Prepare a short session with a clear objective, and note where players hesitate, misread the game’s feedback or give up. Players from outside the team are especially valuable, because the team already knows how everything is supposed to work.

Resist the urge to explain every action. If you are testing whether the game teaches itself, each hint hides exactly the problem you are looking for. Save your questions for after the session. A short questionnaire after each session, with the same few questions every time, makes the answers easier to compare.

Record the device, controls and build version next to your notes; otherwise you will not know later which version a comment refers to. Then separate personal taste (“I’d prefer a different colour”) from problems that repeat across several sessions, and decide which hypothesis deserves the next change.

When is the prototype ready to grow?

Decide before testing what evidence will be enough to continue, redesign or stop the current idea. Writing this down early protects the team from a natural temptation: carrying on with an idea simply because time has already gone into it.

Test the revised loop before adding many levels, characters or monetization systems. Each of them multiplies the cost of changing the core later. Keep a versioned record of what changed and what the tests showed.

A good prototype produces a playable interaction and a documented decision; a short game design document keeps both in one place. It does not mean the full game is ready for production; that comes later, once the production stage has been planned properly. If the evidence says stop, that is a valid result too: the prototype has saved the cost of building a full game around an idea that does not hold up.