Nadral

Seeing a video of this on YouTube convinced me to check it out to the full, wondering if there was an ending. Unfortunately not. (SEE MORE |)

The objective is to find all the keys and their corresponding doors, leading you to the helicopter icon that completes the Mission.

Various items give you points, extra lives and energy. Don't know what the purpose of the lampposts is. You can shoot them out but the enemies can still see you.

Missions are named after letters of the Greek alphabet: Alpha, Beta, Gamma, Delta, Epsilon, Zeta, Eta, and Theta (being the last, then it loops back to that).