Slitherio is a great io game released in 2016. Control a snake, eat glowing orbs to increase your snake size. Your main goal is to become the longest worm in the arena and defeat all the players. If your snake's head hits any other snake's part, you'll explode and the game is over.
When a worm dies, its body will turn into the bright balls (orbs) it was before it died. The player can consume pellets dropped from dead worms to increase their size. These pellets give more weight than the regular ones.