Small games are fun when one repeated action feels good, answers instantly and points at a goal the player wants again. That cycle is the core loop. Test it with grey shapes before anything else: if it is fun as rectangles, art will only make it better.

This guide is for first-time game makers, hobbyists and anyone planning a casual game. Most first games are built the other way round, with menus, a shop and ten levels around a loop nobody tested. The running example is Comet Catch: drag a basket to catch falling comets and dodge rocks.

See it in actionAct, feedback, goal in Comet Catch
Drag the basket, catch a comet, and see a spark and +1 that move you toward a best score. The grey-box version shows the loop works without art. Illustrative example. Use the playback controls or the thin timeline at the top to explore.

In short:

  • Act, feedback and goal are the three parts of every core loop.
  • Short loops come first, long-term rewards last.
  • Grey-box tests show whether the loop works in one afternoon.
  • Weak feedback can make a good loop feel broken.

A core loop is act, feedback, goal

Every core loop has three parts that repeat every few seconds:

  • Act: the player taps, drags, jumps or aims.
  • Feedback: the game answers at once with movement, sound or a number.
  • Goal: the answer moves the player toward something they want.

Flappy Bird is the minimal case. Tap and the bird rises. Pass a pipe and the counter goes up. Touch a pipe and you are back at the start within seconds.

Designers have described this for decades. Raph Koster's book A Theory of Fun for Game Design argues that fun is the feeling of learning a pattern. Dan Cook's essay The Chemistry of Game Design breaks play into small "skill atoms" of action and feedback.

Short loops come before long ones

Successful casual games stack loops of different lengths, and the short ones carry everything.

Loop Lasts Comet Catch example
Moment 1 to 5 seconds Catch one comet, see a spark
Session 1 to 5 minutes One round, ending in a score
Long-term Days Beat yesterday's best score

Many people start with the long loop because it is easy to describe, like unlocking characters. A daily reward on top of a dull catch is still a dull catch. When the short loops work, our article on how streaks work as rewards covers the long one.

Design the loop on one page

Write one sentence for each of these before you build:

  1. Name the verb, the action the player repeats most.
  2. Describe what happens in the first tenth of a second after it.
  3. Say what can go wrong.
  4. Say what number or picture changes on success.
  5. Say how long it takes to play again after failing.
  6. Name the first change, within 30 seconds, so the pattern is not solved.

For Comet Catch: drag to move a basket. A caught comet pops with a spark and a chime. Rocks fall too, and three rocks end the round. Each comet is +1. One tap restarts in under two seconds. After 20 seconds, everything falls a little faster.

That page is the whole first version. Menus, skins and levels wait.

The grey-box test shows fun in an afternoon

Grey boxing means building with plain placeholder shapes, so you test the rules, not the art. Run it in four steps:

  1. Build only the verb, the danger and the score, with coloured rectangles.
  2. Play for five minutes and note when you stop wanting to.
  3. Hand it to two people without explaining anything.
  4. Watch whether they start another round on their own.

If they understood within ten seconds and played again, keep going. If they were confused, the feedback is usually too weak. If they understood but did not care, the danger or the twist is missing. Our playtesting with five friends script turns this into a full session.

Weak feedback hides a good loop

A correct loop can still feel dead if the answer to the player's action is quiet. A small squash, a short sound and a tiny shake make the same tap feel completely different.

Martin Jonasson and Petri Purho showed this in their talk Juice It or Lose It. They took a plain block breaker and added effects one by one, without changing the rules.

Our list of 12 cheap juice tricks collects the cheapest ones. Juice makes a loop louder. It cannot replace one.

Five loop mistakes to avoid

  • Two verbs on day one: tap to jump and swipe to shoot doubles what new players must learn.
  • Slow restart: an ad, a menu and a spinner after every loss turn "one more go" into "quit".
  • Hidden success: a score in a corner nobody looks at.
  • Random punishment: if players cannot tell why they failed, they stop learning.
  • No twist: the first 30 seconds are fun, then the pattern is solved.

Loops in GrowApps games

GrowApps builds real Flutter apps from a chat, games included. For a real-time 2D game, it uses the Flame engine, and its first milestone is a playable starter game in the preview, which it then reshapes into yours.

Turn-based games such as quizzes and memory games use plain Flutter widgets. That order matches loop-first design: describe the loop, play the round, then add the rest. See growapps.ai.

Write your loop page now

Take your game idea and answer the six questions above in one sentence each. If you cannot answer question 6, you have found your first design problem. Then read how to structure a game project in GrowApps to turn the page into a first prompt.

Frequently asked questions

What is the difference between a core loop and a game loop?

A game loop is the technical cycle an engine runs every frame: read input, update, draw. A core loop is the design cycle the player feels: act, feedback, goal. You design the core loop. The engine runs the game loop.

Do I need levels to make a game fun?

No. Many popular casual games have one endless mode that slowly gets harder. Levels are one way to add new twists, not a requirement.

Sources and further reading