Rampart

Rampart was produced by Atari Games in 1990.

Build up a castle using Tetris-like pieces to form a wall enclosing your territory. Next, place cannons, and then use them to fire upon enemy boats or opposite player’s castle! Then it’s back to rebuilding your castle before another round of destruction.

Rampart has three modes of game play, depending on how many players are in the game:
In a one-player game, the player has to defend his castle from an armada of sailing ships. There are two or three types of ships, each type denoted by the color and size of the ship. The larger the ship, the more shots it takes to sink it.

A two-player game presents the players a choice of two different game modes:

A harbor mode where the play area is divided into thirds. Two-thirds of the play area is land (one-third for each player), and the last third is dedicated to water. At the start of each round, the players are given a number of ships in the harbor depending on the amount of land under the player’s control.
A river mode where the play area is divided in half by a river. The players use their cannons to lay seige to the other player’s castle(s).
A three-player game is identical to a two-player game river mode, except that the play area is divided into three equal sections by an inverted Y-shaped river system.