Stack Attack is a game meant to be run along side a Twitch stream. When you launch the game, proceed to the OAuth menu and link your Twitch channel. Once done, setup your streaming app of choice to see Stack Attack with Alpha/Opacity enabled. Then, when you click Launch, you can minimize Stack Attack. In your chat, if linked correctly, you should be able to use the commands !throw and !stats to join games or get a report of your top three caps.
It also supports custom cap graphics. In the Stack Attack game folder, there is a StackAttack_Data folder. In there, a StreamingAssets folder. In THERE, a folder for both Caps and Smashers. Caps being what you see in the tower and that players can collect. Smashers being the coins that are thrown at the tower. Both support Albedo (Main graphic), Metallic (Shininess), and Normal (Ridges and Bumps) maps.
In the settings tab, you can adjust the Max Players (Default 8, game will auto start if this count is met), Caps Per Player (Default 10, the amount of caps a player will contribute to the tower, or be given to contribute), and the Start Timer (Default 60, time before the game auto starts if the max player count is not met)