Here's how to play:

Start by selecting a difficulty level (I recommend beginner at first) then click on the deck to deal cards. Drag the "current player" card to whichever player you want to go first. You can then pass that card between players to change turns.

Goal: use all the cards in both players hands before running out of cards in the deck

The Deck is mostly composed of red and blue numbers 1 through 12

Play cards on either stack in numerical order by placing a card one above or below the top number (ie a 5 can have a 6 or a 4 played on it) 12's and 1's can be played on each other

Roles determine what colors you can play - the same color role has to match colors and the alternating role has to alternate colors

Bridge cards let you jump up or down a number (a 5 with a bridge on it can have a 7 or a 3 played on top)
also: if a stack starts with a bridge then any play can put a 1 or a 12 on it.

Switch cards cause the roles to swap, all 6's and 7's are switch cards

Special cards are played like normal number cards, but then you can play any odd number on an even special or any even number on an odd special (roles still apply)

A turn consists of three phases: draw, play, pass

Draw as many cards as you like up to the hand limit of 7 cards; drawing is mandatory if you need a playable card

Play at least one card or more if you prefer

Pass a card to your teammate

If you have 7 cards and none of them are playable, you are stuck! your turn ends and you cannot pass cards. If both players get stuck, the game is a loss.

The difficulty levels influence the number of bridges: Beginner - 8 bridges, Easy - 6 bridges, Medium - 4 bridges, Hard - 2 bridges, Expert - 0 Bridges.