This is a game based on the childhood game where one goes, "I shot you!", "Nuh-uh! I had bullet proof armor!", "Well, my bullets explode!", "Nuh-uh! I've got a force field!", "Well, my bullets create an EMP field" and so on. The idea is that for every attack, there is an opposite counter, and an even stronger attack that can come after it - to the point where everybody is nuking planets from orbital space platforms. A special thanks goes to my wife for planting the seed for this idea.
Play begins on a barren field. All your units, which are of only a few basic types, begin on the board and have standardized movement. Each player is dealt ten cards from the deck. Each turn, they can move up to 3 and either place a card or remove one.
Each card has a leveled effect which will affect whatever row or column it is attached to. You must start with a level 1 card for each block, but you can overwrite it with a level 2 (and then a level 3) card if it is the same type. These cards are stacked on top of each other respective to whatever row or column is affected.
For instance, if you place a level 1 Lava card on a row, it might make the middle three blocks into a lava pit. Any unit standing on a block that becomes a lava pit will take some damage and jump back to the previous row (continuing until safety is found). The first and last row are immune to effects, so you can't place cards there and any column cards place will not affect them.
Player two decides that he wants more laval, so he upgrades the row to a level 2 Lava card. This increases the amount of lava on that row. On Player one's turn, he upgrades it to a Lava 3 card, reducing the entire row to one big steaming stream of lava.
One of the players decides that he'd rather like to cross the lava, so in one of the columns, he puts a level 1 bridge. This allows him to create bridges across any pit obstacle (lava, water, etc) in that column. Unfortunately, other obstacles, like cliffs (requires staircase) or walls (needs cracks) need a different solution. So, the player turns to a level 2 bridge AND staircase card. This will open up any pit or cliff obstacles in the row, but not affect wall obstacles at all. A level 3 counter could have bridges AND staircases AND cracks.
There should be an order of operations, so that when a column of walls runs into a row of lava, you know which obstacle should take the square.
If you elect to remove a card rather than play one, you simply remove the top card from the stack, and the previous card is now active. You can't go from all to nothing, you've got to slowly go in reverse. To prevent the game from become a back and forth or playing and removing cards, a card should have a timer, like three rounds, during which it cannot be removed. A timer can also be applied to cards, such that no effect will last longer than ten rounds or something.
The entire stack must be removed before one can place a card of a different type in that row or column, and again, it must begin with a level 1. This means that if Player One removes the last card from the stack, Player Two will have the first option to place the new card there.
Units can be escalated in addition to the field. You can apply a unit effect to each different type, and all units of that type are upgraded. Like field effects, unit effects can upgraded to level 2 and level 3 versions of the same type - though there might be a tree of possible upgrades rather than a one to one thing. For instance, the body armor may be upgradable to knight armor (poor against ranged) or to a personal shield generator (poor against melee), and each of those may have their own level 3 version.
Each upgrade usually buffs one aspect of a character while making another worse. So you might increase defense to melee, but ranged will kick your butt harder. Or you may have fire arrows which do damage over time, but have a smaller range. The point is that you are specializing your units, and your opponent is likewise specializing his own. Going to level 3 may really improve your unit, but if you need to change direction (like your opponent build a unit that exploits your weakness) it will take three turns to back down to basic unit to start a new upgrade path.