Easy data structure and algorithm practice puzzle.
Given a color as [r, g, b], each from 0 to 1, return its brightness, rounded to 4 decimals: 0.2126 x r + 0.7152 x g + 0.0722 x b. The weights aren't equal because your eyes aren't. Green looks much brighter than blue at the same strength.
Solve it three ways: snap the jigsaw pieces together, fill in the blanks, or type it from scratch against the tests. This one is free.
Every line of the solution comes with a note explaining why it is there, and a step by step replay shows the code running. At level 3, where you type it yourself, you can ask for an AI mock interview on this problem that ends with a hiring manager's scorecard.
Then grow it into a real project with the Software Engineer button: this puzzle becomes the Frame Smoothing Rig, a pipeline you can run and download. See every Software Engineer project.
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