This is The Pyramid by Richard Langford, Where you walk towards your spaceship and get inside, and get Ready for action!
A pyramid shows your Level Progress throughout, including Score and Lives information (this screen also shows if you lose a life by touching an enemy), then you are put into the First Level
The aim of the Game is to collect the Diamonds to then put into one of the holes at the bottom of the screen, these are fragile and will break easy, if they for example, touch an enemy, or you touch them accidentally
Once in the first level, Enemies will spawn in, in this case, from the top, so do not stay near the top initially, when a circle appears, an enemy will follow, and then proceed up and down the screen, until you shoot it
Every so often, various items will drop from the top of the screen, like Diamonds, which you need to aim at one of the bottom blocked exits, as you will need 3 to open up the exit, which then allows you exit the current level and proceed down the Pyramid line-by-line on your way to the bottom
Other items what fall down add Points to your score, and you also get Points for shooting enemies as well, Can you reach the bottom of the Pyramid?
This game is well designed, and proves yet again, what can be accomplished with AMOS, while simplistic in design, there is a large set of levels to play, and you could easily play this for a few hours quite easily
Please visit the Langford Video website