Wouter's amazing math card game (2 players)
Note: this game I have actually implemented/tested, and it can be quite deep and a lot of fun.
The deck consists of 2 sets (red and blue) of 35 cards each, for a total of 70 cards.
The red cards are:
To start a game, each player shuffles their deck of 35 cards, and lets the other player “cut” it (like in poker).
Each player draws 6 cards to start. Before your turn, a player ALWAYS has 6 cards, except for the end game when cards are running out.
Players take turns. If a player has not played any cards on the table yet and can't play any, he puts his whole hand on the bottom of the pile and draws 6 new cards.
Normally, on your turn, you play 2 cards out of your hand, and then draw 2.
Ways to play a card:
Sequences are evaluated strictly left to right, and modifiers MUST be resolved before the final result is computed (in algebraic fashion). For example:
 + 2 cancel * 5 invert * 2 swap =
is evaluated like:
4 (4, start card) 4 + 2 (6, operator + number) 4 (4, cancel the +) 4 * 5 (20, apply multiply) 4 / 5 (0, apply invert, multiply becomes integer divide) 4 / 5 * 2 (0, apply multiply) 4 * 5 / 2 (10, swap the divide and the multiply) 10 (10, seal the sequence)
Important: Your two cards played must be to seperate sequences (!).
Most important rule: a player on his turn MUST play the maximum number of cards he can, in whatever combination. If you CAN play 2 cards, you MUST play 2 cards. If you can play only 1 card, you must play it. You must play the cards in whatever order maximizes the amount of cards played.
If (once you have at least one card in play) you are able to play less than 2 cards, you put up to 2 cards on the bottom of your pile such that always 2 cards leave your hand per turn. Your turn should always end with 4 cards in your hand, such that you draw 2 to get 6.
The exception is once your pile is empty, you don't get to draw anything. The game is over once both players are out of cards, or, in rare cases, when both players both had a turn in sequence without being able to play nor draw new cards.
Once the game is over, all 8 sequences are evaluated, and scores tallied (you receive the sum of all sequences that started with a starter cards of yours). highest score wins.