Cycling Element

Select an element from an array with the catch being: it must keep changing to the next one!


A trending design pattern you might have noticed even on my homepage, is to have some of the copy in a "Hero" section keep changing. Next.js for example opens with this:

How would we recreate this? Are we limited to text, or can we cycle through anything? Numbers, components, even functions?

We will explore with this challenge!


Let’s make a game!

You are meant to progress through the list items step by step. Completing all of MVP leaves you with something usable you can deploy and show.

Making it through all stretch goals leaves you with something fun to message your friends to try out!

The FeaturedPreview above, the button you may tap to affect your score, is a work-in-progress based on me going through the spec live, on the Twitch stream.


1. Create a prominent header which cycles between the following text:

  • “The best game for developers”
  • “The best game for nerds”
  • “The best game for training your twitch reflex”
  • “The best game for hand-eye coordination”
  • “The best game for you

2. Create a button with copy alternating between “hit to win” / “hit to lose”

3. Clicking the button while it includes “win” adds 1 to your score

4. Display said score prominently above the button, below the header

5. Clicking the button while it includes “lose” subtracts 5 from your score

Stretch Goals

1. Have the changed part of the copy in the header “animate in”

2. Game alternates between three “buttons” that have no copy: They just look different. For example: “green circle”, “grey circle”, “red circle”, but feel free to be creative, maybe use sprites!

3. Endless mode:

  • hitting the “green circle” adds one point
  • hitting a “grey circle” removes two points
  • hitting a “red circle” results in “Game Over”
  • The “Game Over” screen shows the high-score even more prominently
  • “Game Over” screen has a button to restart the game
  • Not clicking “green circle” before it changes removes one point

4. High-score mode:

  • “Game Over” screen as above, after we’ve gone through 30 buttons
  • Users can choose between “short” / “medium” / “long” sessions

5. “Random” modes:

  • instead of predictably alternating between the buttons, vary the order in which they appear
  • Keep the ratios the same: if a “long” High-Score session is going to show 300 buttons it has to be 100 “green”, 100 “grey”, 100 “red” buttons

Starting points

Code Sandbox

If you wish to give this a try in React, all you have to do is use this Code Sandbox!

“Official” git repository

To work with your own tools but with React, testing, and styling via Tailwind.css already setup for you, you may checkout this repository:

  • pages/coding-challenges/cycling-element/playground/index.tsx is a mostly empty React file. Feel free to work in there, and/or create extra components in the components directory, and write extra tests. Any file ending in .test.tsx will be picked up when you run yarn test --watch
  • yarn dev will start the hot-reloading development server, and you’ll be able to see the results of your work at http://localhost:3500/coding-challenges/cycling-element/playground

This is a more realistic workflow, as most of the time in software engineering, you are adding features to pre-existing codebases.

MacGuyver mode

You may create your own solution in anything you’d like, and use the contact form to submit a link to wherever you’ve made your source code available! It’d be great if it were also deployed somewhere like Netlify so everyone can have a play!

Lone Ranger

And, of course, feel free to give this a try even if you have no intention to submit anything to me for feedback. The point of this is for you to learn, and I’d love to help more; but I can step out of the way as needed.

Demo solution

There is a solution-in-progress over at /coding-challenges/2020/cycling-element/demo. As mentioned before, you may catch the Twitch stream to see me go through the spec live!

It’s not meant to be “the one true solution”, but it is using React with hooks 😄

I am trying to have fun with mine, make sure to have fun with yours!