One to three coins can be put in the slot machine each play. One coin will only count the center row across, two coins will count all three rows across, and three coins will count all three rows across as well as both diagonals. The reels stop spinning when the player presses the A button.
In the Generation II games, several things can happen when 7's appear on a reel:
When one 7 displays on the reels, sometimes the second one will spin down to a 7 as well.
Several Golem will drop when two 7's are lined up.
The third reel will move by itself when two 7's are lined up. It will either line up and pay out the jackpot, or end up one space away from lining up to tease the player.
A slot machine in Japanese HeartGold and SoulSilver
Only the Japanese version of Pokémon HeartGold and SoulSilver has slot machines. These slot machines play differently than in the Generation II games. Pressing A stops the reels from left to right; however, the Control Pad controls both coin insertion and reel starting. Additionally, slot machine payouts can actually vary per machine, and are typically more in line with the Sinnoh games as opposed to the original Generation II games.
As players use the slot machine, a Smeargle depicted on the top screen and seen painting can change the background of the top screen's monitor, and any change in background changes slot effects. A green background signals normal play, a red background signals that it's easier to obtain a 7 or Poké Ball, and a blue background signals that it's easier to obtain a Pikachu or Marill.
The jackpot for three 7's is 100 + 2x, while the jackpot for three Poké Balls is 100 + x, where x starts at 0, may increase whenever a non-jackpot symbol is lined up, and resets to 0 after every bonus game.
A bonus game is started by winning a jackpot. Lining up three 7's starts a 15-round bonus game, while three Poké Balls will trigger an 8-round bonus. In this bonus game, players attempt to perfectly line up a randomly chosen one of Johto's starter Pokémon, and the machine may provide some assistance. Bonus game payouts vary depending on success, as well as the slot machine's speed during bonus games. At the end of a bonus game, the background automatically becomes red. This lets players "chain" together jackpots and bonus games; however, the bonus game difficulty increases (up to a maximum) with each chained jackpot.
The card flip minigame is exclusive to the Generation II games. The player can pick either a card or a group of cards in a manner similar to Roulette. The 24-card deck has cards numbered from one through six, with suits marked by illustrations of Pikachu, Jigglypuff, Oddish, and Poliwag. Bets can be placed in a variety of ways, with the final payout depending on the bet method.
The game features a five-by-five grid of tiles, underneath which are hidden numbers (which multiply the player's score if located) and Voltorb (which Selfdestruct and cause the player to lose all points). The player has a chance to figure out where the Voltorb are located by using the clues provided: the number of coins and Voltorb in each line and column are noted at the sides of the playing field. If the player can find all of the 2× and 3× multipliers, they will be able to advance to harder levels. Winning at this game, as before, will earn the player Coins, which can be traded for prizes.
The Goldenrod Game Corner appeared in Gligar Glide, where Gold was seen playing a game of pool there. However, as soon as it turned out that Gold was cheating by using Aibo's Poké Ball as a disguised white ball, he was thrown out of the building.
Although the Goldenrod and Celadon Game Corners were changed in the non-Japanese releases of Pokémon HeartGold and SoulSilver, all versions (Japanese, Korean, and Western) have every map of the Game Corners: in the Japanese versions, the maps related to Voltorb Flip and Mr. Game are unused and have no events or warps programmed, while the Korean and Western versions have the original maps with their warps intact, plus the event to interact with the clerk is still present and the interface used to buy coins is functional and was translated. TM78 (Captivate) also remains in the unused Goldenrod Game Corner in the Korean and Western versions, and the slot machines in the leftover maps trigger Voltorb Flip in these versions.
The internal data for Pokémon Gold, Silver, and Crystal shows there was plans for a card memory game where the objective would have been to clear board of all matching cards and there would have been three difficulties to choose from.