Looking for a game.

Hi, I'm looking for a game described as : You start at space (platform game) where in the back ground you can see some planets. You have a laser gun shoots a long laser beem. The first monsters are white walk directly to you and when you kill them you get gold coins out of them. At the end of the floor you find an alavator that you have to stand exactly in the centre to get in it and go to the next floor (down). You can jump too and there is some sort of store to buy weapons like : grenades, exploding arrows and in later levels you can get a high jump device. I'v been looking for this game for a long time and never get any clue. Please help me to find this game.