The Wit.nes is an NES demake of the 2016 puzzle game "The Witness". The game features a various collection of grid puzzles, with each one unlocking a new puzzle or a new area on the map. Some puzzles will have different symbols that signify different ways a puzzle has to be solved, such as separating colored dots or drawing different shapes with each line.
Despite being fully playable, The Wit.nes was only released as a demo and never saw further updates, despite the demake having the support of Jonathan Blow, the creator of the original game.
brunovalads solves all the puzzles and opens up the big door at the end in record time.
You can watch this run being played back on a console.