Coins are the in-game currency needed for upgrading different in-game parameters such as parts. You also need gold to skip enemies in Quick Fights.

There are currently four ways to get coins:

1. Win Championship
Complete Championship Stages and get yourself some gold, as well as a Skill Point, Gems, and a Supply Box.

2. Defend against Championship opponents
If your machine is powerful enough, it will bring you coins even if you are offline!

3. Open Boxes
Earn boxes by completing the quick fights and stages in the championship. Each box have a certain amount of coins!

4. Sell Parts
If you don't have enough gold, you can sell one of your parts. To do it, drag the part to the lower right corner of the screen. Please note, that this action is irreversible. You will lose the sold part and it won't be possible to recover it.

If you don't have enough gold to upgrade the part, you can spend Gems instead.