Lists are somewhat ordered from best to worst.
Crossed list items means I finished the game.

playground

• css playground https://playcode.io/css

multiple games

• https://codepip.com/

online / competitive

• https://play.battlesnake.com/
• multiplayer replication battles https://cssbattle.dev/

general

• guess the correct style sheet
• https://css-challenges.com/

select

• https://css-speedrun.netlify.app/
• https://flukeout.github.io/
• https://codepip.com/games/css-scoops/ (paid, $6/m or $99 lifetime for all games)

flexbox

• https://mastery.games/flexboxzombies/
• https://preview.webflow.com/preview/flexbox-game?preview=d1a26b027c4803817087a91c651e321f&m=1
  couldn't beat last 2 lvls
• http://flexboxfroggy.com/
• (tailwind) https://knightsoftheflexboxtable.com/
• https://codingfantasy.com/games/flexboxadventure
• http://www.flexboxdefense.com/ kinda trash and buggy

grid

• https://gridcritters.com/ paid, expensive
• https://codingfantasy.com/games/css-grid-attack
• https://cssgridgarden.com/
• https://gridbyexample.com/
• https://css-tricks.com/snippets/css/complete-guide-grid/
• https://james-priest.github.io/grid-critters-code/?pg=1