In River Rats you take on two of them either alone or as a team like on a casino table where the goal is to have a higher hand, but there are no bets and actual card play is involved; there are even abilities each side can use.
Each player takes an ace that gives them an ability they can activate, or if you play a card of your suit you can use that power instead, the enemy also has a king up their sleeve and rats' suits also give them an ability that affects the table.
Players draw a card from the deck or a face-up market and play cards to form a hand. Once the river is laid down, it's showdown time, and all cards are shown. Whoever wins places the other team in debt, any side that gets 5 debt is out of the game. When you beat an enemy rat you get an extra advantage.
To make gameplay more than just playing for the best possible hand, the value on a debt card signifies the hand you need to make to acquire a joker, which you can use as a true wild card.
Interestingly, solitaire play doesn't require any different preparations from the multiplayer game and yet the gameplay can differ depending on the number of players, with co-op being a coordinating of powers while solitaire play is more tactical with only one available set of abilities in play to use against another. Solo play is just drawing and playing the five best cards you can make while making best use of your abilities. In co-op no one is allowed to divulge card information and with more abilities in play the team must reach their goal together as soon as their hand is made.
The risk in acquiring jokers is akin to a platformer: is it worth risking a wrong move to get a bonus? For higher debts the difficulty of the hand is itself the risk, for lower debts it's possibly losing the round (The lowest debts require a straight, though the requirement has to match exactly).
Beating the first enemy means a boon on the second round, though the second enemy is otherwise the same save for a different ability. Would it be better if the second enemy has a stronger fight for a level 2 is not something I'm ready to answer, as it is there are enough abilities to have to check.
At least it's more than simply playing out cards to make a hand, and already things are happening on the table that aren't beyond your control, just by that alone it's way more involved than any game at the casino that isn't outright poker.