Gigascreen
A Spectrum trick that swaps two images every frame so the eye blends them into more perceived colours.
By flipping the screen contents exactly in step with the 50 Hz interrupt, the retina merges two attribute sets into intermediate colours the hardware cannot really show — a way to dodge attribute clash and reach far more shades (sometimes marketed as "gigacolour"). The price is visible flicker and a CPU forced to keep rock-steady timing against the raster beam. The technique belonged to the 128K era and the demoscene rather than to games, and is kin to Amiga interlace flicker and temporal dithering in general.