Head Soccer is exactly as it sounds -- two heads facing off in a 2D version of soccer on a short field. The style of play is very different from what you'd expect in a soccer game, but it somehow works perfectly for short, fun bursts of play on your phone. While there are some dated components, most notably the graphics, which have not yet been upgraded for the retina screens, the game plays well and is fun.
Installation and startup are fast and there are no extra downloads or log-ins required to get started. You can immediately jump into an arcade game or you can start a tournament, play survival mode, join a league, or play multiplayer over Game Center or Bluetooth. It all runs smoothly and without much delay, though again, the graphics look dated and a bit washed out, which can be detracting with so many crisp looking games on the App Store these days. The game, itself, is two characters jumping and kicking to get the ball into the opposing net. The field is 2D and you can only move forward and back so it's a very stripped-down version of the game and the scores will be very high as a result, but the fast pacing and range of options make it accessible and fun for all ages.
If you enjoy short, quick bursts of gameplay or want a new sports-style game to play against friends, consider Head Soccer. The app could use some updating and the controls are a bit unwieldy if your opponent knows their stuff; but in casual settings, it's a lot of fun and very rewarding for a free app.