When you get a winning combination in the main game mode, the Gamble button in the lower part of the game control panel will light up. You can use it to enter the risk game mode. In this round, the playing field displays five playing cards. The cards are lying face down, so you don't know anything about their team. You can choose to bet the sum of the previous earnings (press the double button) or just the lower half (press the double half button).
Once you make your choice, you will see one of the cards displayed. Now you have to choose one of the remaining four cards. If it ranks higher than the card's ranking, you will get double the reward. You can press the collect button to keep the new amount and exit the risk game, or continue playing the game to get a chance to further increase the bonus. You can use the "Collect" button at any time until you get an error and choose a card that ranks lower than the dealer card. In this case, you will lose the risk game and you will not get the original return.