Start with a standard deck of cards. Remove the jokers. Set aside the kings, face up:
Choose any king. This is your king and your suit. Turn this king face down among the other kings. Here I chose the king of diamonds:
Leave the kings aside and shuffle the rest of the deck. Deal three cards, face up, next to each other at the edge of the table. This is your arsenal:
Turn over the king stack onto the deck. All cards in the deck will be face down except for your king. I often find it helpful to manually insert the kings into the deck at random locations like this (my king is sticking out to highlight that he remains face up):
Shuffle the deck. Deal cards, face down, in a 7 by 7 grid. Of course, your king will still be face up:
The 7 by 7 grid is the map. Face down cards are parts of the map that you haven't discovered yet. My initial territory is any face up card matching my suit. When you start, your territory is only a single card; namely, your king.
To win you must discover the entire map and make it your territory. Try to do it in as few turns as you can. On each turn, you can perform one of the following moves.
Turn all cards face up which are adjacent to a chosen face card of your suit. A card that's fully surrounded has 8 adjacent cards. A card near the edge may have fewer adjacent cards.
Here I've used my first move to explore the map around my king. I expanded my territory by one square (the 6 of diamonds) and uncovered four squares of enemy territory.
You can swap a face card of your suit with any other space in your territory. In the image above, I could move my king to the right by swapping him with the six of diamonds. You don't have to travel to an adjacent space, that's just how the layout appears in this image.
You capture a space, making it part of your territory, by attacking it with a card in your arsenal. The card in your arsenal must have the same suit as the card you're attacking. Your arsenal card must also have a higher rank. Once a card is captured, remove it from the map and place it on top of the arsenal card that captured it. The captured card is now your arsenal card.
An arsenal card of your suit can be used against any suit. Although, once it has performed its first capture, it's permanently fixed at that new suit (since the captured card is now your arsenal card).
For example, in the position above I used the eight of diamonds to capture the six of clubs. That gives this position:
The vacant space in the map is now part of my territory.
The final move available during a turn is to conquer an opposing king. To conquer an opposing king, he must be face up and at least 51% of his adjacent spaces must belong to your territory. For example, if a king has eight adjacent spaces, at least five of them must belong to your territory.
Once you've conquered an opposing king, remove him from the map and place him near your arsenal. All face up cards of his suit are now part of your territory too.
Tech Tree Variant
Many 4X games have a technology tree. Learning a technology grants the player a new ability. A tech tree can be added to 4X Solitaire with a slight adjustment to the rules above.
After dealing your arsenal, but before shuffling kings into the deck, choose one arsenal card to be your technology. The technologies are determined by the suit of the card you choose:
- spades - flip over one card anywhere on the map
- hearts - conquer with only 50% of a king surrounded
- diamonds - explore an entire row/column instead of adjacent cards
- clubs - capture any enemy card, except a king
Set your technology card aside and deal another arsenal card in its place.
If you choose to play your technology card during the game, you can play it only once and using it counts as a turn.