Treasure Chest lets you unlock rewards on each run.

At the beginning of each run, you start with a LVL 1 Treasure Chest, which is displayed at the bottom of the screen.

As you pass checkpoints, destroy buildings and zombies, or collect items - the collected coins, items and rewards will fly directly into the chest icon, and the progress bar will fill up!

After the run has finished, you are presented with the chest on a dedicated screen.
Coins will increase in amounts based on the level of the chest itself. Chests can ONLY be opened if you have AT LEAST ONE KEY