This page describes the Game Corner in Essentials.
The Game Corner is a unique building where the player can play with Slot Machines and Voltorb Flip. The Lottery is usually located there as well. The player can earn coins from games and spend them on prizes. The Game Corner in the example maps also features examples of the Triple Triad mini-game.
There are typically two separate buildings to the Game Corner: one for the games, and one where you can exchange coins for prizes.
A Coin Case is a Key Item that holds the player's Game Corner Coins. Coins are not actually stored within the Coin Case, though. The Coin Case only serves as a way to restrict access to the mini-games: you cannot play or buy Coins if you do not have a Coin Case. Using the Coin Case from the Bag displays the current Coin amount.
The amount of Coins the player has is stored in the variable
$PokemonGlobal.coins. You can change this amount at any time, even if the player does not have a Coin Case yet. The maximum amount of Coins the item can hold is specified in the script section Settings.