Programma Reanimator Skachat
Atmega is quite an old processor, so doesnt really have the hardware to drive neopixels neatly, at least if you want to do anything else. For driving neopixels, I would suggest moving to another processor family such as STM32, where you can drive multiple neopixel streams with very low overhead using a timer and DMA straight from C. No asm required and you will have most of your processing power still available for other tasks. Offtopic, but I would guess RP2040 also would do a nice job using its programmable PIO and 2 cores!
programma reanimator skachat