GTA: Viking Valor
A long long time ago, there was a large gem, which the people so admire. But, the greedy king took it for himself. Now brave viking promise to return the gem to the people. The king would not want to happen, so he declared a war against the viking. The game is played via mouse and the idea here is not to let the enemies closer to your ship. You can get gold from the fallen enemies. You can use the money to buy traps or to upgrade your weapons. The enemy would come in wave and after successfully defending the ship, you would get gems based on the damage your ship has taken.