An original card game by Kenneth P. Langer
Objective: Be the first to defeat the enemy Ruler by tearing down their castle, while defending your own. You play against the computer.
Each side has its own 52-card deck. One King or Queen is set aside as that side's Ruler. The rest is shuffled; each side draws a starting hand of 6 cards.
Each turn you get 2 actions, chosen from:
Red cards build structures. The Wall needs 5 single red cards (one per segment) — no red card matching your Ruler's rank may be used on the Wall. Once the Wall's 5 segments are all built, you may build two Towers (2 red cards each) at its ends. Once both Towers are built, you may build the one Keep (3 red cards) behind the Wall.
Any built structure can be fortified by stacking more red cards on top: +1 for the Wall, +2 for a Tower, +3 for the Keep. Your Ruler can also be fortified with matching-rank cards. Fortification layers must be defeated top-first. Once a structure has been armed with a weapon, it can no longer be fortified — arming is always the last thing you can add to a structure.
Black cards arm a completed structure with a weapon — once armed, nothing more can be added or removed from that structure.
Pick one of your armed weapons and a target structure on the enemy board. Roll dice (1 for a Ram, 2 for a Ballista, 3 for a Catapult) and total them. Each weapon also has its own trick, so the choice of which structure to arm is a real tradeoff between cost, reliability, and raw power, not just "bigger is always better":
The target number is the value of whatever is physically on top of that structure: if it hasn't been armed yet, that's its topmost red layer (a single card for a Wall segment, the combined value of both cards for a Tower, or all three for the Keep); once it's been armed, the weapon's own black card(s) sit on top instead and set the target number. Number cards count face value, Aces count 1, face cards count 6. Beat the number and you capture that top layer (and the weapon along with it) into your discard pile. You may also combine two of your weapons against one target (their dice and traits both apply) — but that uses both of your actions for the turn.
Once all enemy Wall segments, one Tower, and the entire Keep have been destroyed, their Ruler becomes attackable. A Ruler (and each fortifying card on it) counts as 10 points and must be defeated layer by layer, just like any other structure. Destroying the base Ruler card wins the game.
This and other original games can be found in the book 52+ New Games for Those Old Cards by Kenneth P. Langer.