SDI2040 is a Space Invaders clone. It doesn't add many new features. There are some subtle differences, like the fact that the enemy ships are smaller than usual so they are a bit trickier to hit. The game plays decently, and includes functional graphics and sound effects, but nothing particularly exciting. The controls may take some getting used to, since your ship will continue to move in one direction unless you hit the down key or move the opposite way.