My partner and I were watching the premiere episode of Severance Season 2. We were, like most viewers, wondering what Macrodata Refinement actually is. (If you haven't watched the show, no worries there are no spoilers here).  I mentioned off-handedly that the MDR interface would make a cool variant of solitaire. She looked at me and said how much can you get done by 3pm? The rest is history. 

The game is like solitaire: You must stack the suits. However, unlike solitaire, you can actually see the PIP values of all cards. You mouse over each number/letter to see which suits it belongs to.  Also, you play with multiple decks... and its timed. 

It's built with Vanilla JS/CSS/HTML. I learned about the transition property in CSS. This property makes it easy to do smooth transitions between CSS states like hover. To create the quickly-bright and slowly-fade process you set the transition time on the class to how long you want the item to fade out. Then, you set the transition time on the :hover class to how long it should take to fade in. This one CSS property combined with a little bit of JavaScript is used for all the UI flair in the game.