I played more advanced and immersive shoot em ups 2 decades ago.
Games such as R-Type perfected this formula over 20 years ago, and were taken to the next level by games such as Project X, Agony and X2 some years later. These games boasted beautiful scrolling graphics and backdrops, variation between levels, with different themes, weather, underwater sections, super fast scrolling levels and more. Zeit Squared on the other hand, has none of this. Literally. Not even scrolling graphics and or varied backdrops. It's like they took the original formula and reduced it to its basics.
The one redeeming feature of this game, however, is it's music. It has an oldschool synthy vibe which is really soothing to listen to. Personally, I would much rather buy the soundtrack than the game and stick with my Amiga and 32 bit console emulators.