@domi The code: - Sets ES:AX to *[DS:SI]. For a COM exe in DOSBox this resolves to AB48:04C4. - Thanks to real mode, segment AB48 happens to include all of B800:0000 - B800:0FA0, AKA the text display buffer. - The code loops through every 16-bit word in segment AB48 - AX is incremented by current word + the word 82 spaces behind (AKA one full horizontal screen row + 2) - AX is divided by 4 - AX is decremented by 1 - AX is stored into ES:DI, DI is incremented by 2 Result: a moving, fading pattern