In between races, you'll be able to upgrade your cars with cash earned while racing. There is also a tiered racing system that requires you to earn stars in order to unlock tiers of cars and upgrades. Upgrades include top speed, acceleration, nitro efficacy, and handling. Stars and cash don't come easy, so if you really want to advance in Asphalt 7: Heat, you're going to have to commit to competing in a lot of races.
You also have the option to race against up to five friends on a local network or online. In this latest addition to the franchise, multiplayer has been fleshed out a bit more, with a full stat-tracking system so you can compare your stats with your friends. In my testing, I was able to get online immediately and had a smooth racing experience, but that could be because the game is so new.
Lastly, like many modern games for iOS, Asphalt 7 gives you the option to buy your way to the top (a practice I don't agree with). In-app purchases let you buy both stars and cash, so if you're willing to spend the money, you can upgrade that way, though it doesn't seem like it would be as much fun.
Overall, Asphalt 7: Heat is another solid arcade racing game from the popular franchise, with enough new content to make it a worthy purchase, especially at 99 cents. If you like arcade racing or any of the other titles in this series, you should check out this game.