The exercise was developed using React and was bootstrapped with Create React App. For the purpose of animating the bouncing balls, two React components are being used - Animator and Canvas.

The toplevel component is the Animator whose responsibility is to control the creation and animation of the moving objects.

The Animator component renders the Canvas component, whose responsibility is simply to draw the objects on a HTML5 canvas element.

The movement physics of the animated objects is implemented inside the Ball class. This class calculates the movement adjustments (deltas) in each frame based on a starting position and velocity of the ball. The ball class is also responsible for drawing it's outline on the canvas.

The Animator could easily animate other types of objects (images, rectangles, etc), as long as they implement the draw and move methods.

Collision detection between multiple moving objects is implemented in the CollisionDetector class. The collision detector works on the basis of splitting the canvas into a grid, each cell sized as the diameter of the moving object. The collision detector stores the presence of the moving objects into the cells of the grid. This way when a moving object changes its position, we can check if the grid already contains an object on that position. If so, it means that a collision has occurred and the velocities of both objects is changed accordingly.

In the project directory, you can run:

Runs the app in the development mode.
Open http://localhost:3000 to view it in the browser.

The page will reload if you make edits.
You will also see any lint errors in the console.

Launches the test runner in the interactive watch mode.
See the section about running tests for more information.

Builds the app for production to the build folder.
It correctly bundles React in production mode and optimizes the build for the best performance.

The build is minified and the filenames include the hashes.
Your app is ready to be deployed!

See the section about deployment for more information.

Note: this is a one-way operation. Once you eject, you can’t go back!

If you aren’t satisfied with the build tool and configuration choices, you can eject at any time. This command will remove the single build dependency from your project.

Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except eject will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own.

You don’t have to ever use eject. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it.