Mario Kart Tour is Nintendo's most popular mobile game launch ever, with 20 million downloads so far. Here's what it's like to play.

Mario Kart Tour can only be played online and requires a Nintendo account to keep track of your progress.

Races are divides into a series of "cups." Each cup I played had three races and a challenge at the end.

Before each race, you'll choose a driver, cart, and glider, then you'll pick the speed you want to race at, with 50cc being the slowest, and 200cc being the fastest.

Using specific characters or equipment can give you added bonuses in certain races. Unfortunately, you'll have to unlock them first.

Controlling Mario Kart Tour is easy — your car will move forward automatically and you use the left and right sides of the touch screen to steer. I prefer advanced mode, because drifting can give you an extra speed boost.

While the names make it seem like you're playing against real people, you're actually just racing computer-controlled bots. The faster the race, the tougher your competition will be.

Multiplayer will be added to Mario Kart Tour in a future update, so for now you'll have to be satisfied beating your AI opponents.

First, you'll earn some experience points to improve your driver and kart. Increasing your driver's level will help you earn more rewards from races.

The Bonus Challenges at the end of each cup require you to use a specific driver to complete the challenge during a single lap.

Depending on your score after each race or challenge, you'll earn Grand Stars that unlock new cups.

Between races, you'll start to see the differences between Mario Kart Tour and its classic counterparts. There are all sorts of microtransactions encouraging you to spend money to unlock new items.

For $4.99 per month, the Gold Pass will let you unlock items faster. You also need it to race at 200cc, the fastest and most rewarding speed setting.

You can also buy rubies in huge packs worth up to $70. If you spend five rubies, you'll unlock a random item.

The Daily Selects offer a random collection of items each day that you can unlock using coins you collect in races. However, you can only collect a maximum of 30 coins per race.

If there's an item in the Daily Selects you like, you can also spend rubies on a special race called coin rush that lets you collect hundreds of coins at once.

Finally, the game offers a rotating gift set that includes unlockable items, rubies, and other collectibles for $20. The set will change every two weeks.

In the end, Mario Kart Tour is still pretty fun to play, but the constant grind needed to unlock new drivers and courses left me a bit disappointed.