The flickering of the image was purposeful, it was supposed to resemble the loading that occurs in the ZX Spectrum and C64. After that, the picture is also intentionally drawn during loading, and then the color is added (this is usually the case of images loaded on the ZX Spectrum, this is due to the construction of image memory in this computer). To observe this effect, read the .atr file without accelerating the disk drive. Image is the conversion of the original, has 8 colors.
The game works in the PAL and NTSC system, of course in NTSC it will slow down more often, while the colors are loaded during loading, so that both versions look similar.
People with rapidus will be satisfied, because on it the game should not slow down, it is also expected to use additional memory which will speed up the game on ordinary cpu.
Sound effects are original samples from ZX Spectrum converted and reproduced on Atari, they sound almost identical.
The game thanks to Antic and dual buffer technology runs a bit faster than on ZX Spectrum, switching frames occurs at any moment of the screen (no need to wait for the drawing to finish).
I attach the version without flickering.
Thanks to MariuszW , Jose and Solaris104 for help with conversion.