Agar.io vs Starve.io
Agar.io
Agar.io is one of the very first and very popular IO game. Players in this game play as cells that have the unique abilities to eject mass and divide as they fight it out in a 2D arena. Despite being rather minimalistic, the arena itself contains plenty of "food pellets" that you can gobble up to expand your cell mass as well as other obstacles that may either help or obstruct you when you encounter an opponent that you have no way to beat. The game is not only very addictive and competitively casual; it is incredibly strategic and players that excel in it need to have excellent aim as well. You can even customize your cell with a variety of pictures (mainly fun memes or countryn flags), colors and more!Agar.io is definitely a game that will render any productive time you may have into an unproductive one. If you're looking to pass time, this is the game to play!
Starve.io
Starve.io is a unique IO game mainly because it is more of a base-building and survival game rather than just a hack-and-slash arena. In this game, you will need to collect resources and turn them into useful items which will marginally improve your chances of survival. The crafting aspect of the game is very much simplified but it can still take you a while to figure out crucial crafting details like how much resources you need to create a certain item. Also, a quick tip if you will - grab as much food and wood as you can at the get-go.As a survival game, there are several important "meters" that you will need to keep an eye on, such as temperature and hydration. Hunger also something that you will need to frequently deal with, aside from other potentially hostile players as well as other monsters like vampires and zombies if you happen to play its other game modes. There is even a "hunger games" version which frankly feels a lot like a battle royale game.
Unlike many other IO games where players are always pitted against one another, Starve.io is a game in which you can actually choose to coexist with other players rather than just swinging whatever weapon you have in hand at anyone you see... though, many players still do that pretty often, especially those better-equipped ones.