I completed 9 levels and decided to give it a rest.

I completed the level.

You too young for the old arcades then?

It's really easy to complete when the invaders never drop down at the end of each line. Nice tribute to the game but fatally flawed.

They do drop down but not every pass.

In fact they drop down a row after some time and every time a row of invaders has been cleared. But they are to stay above the error code by design (the code always being the center of the action).