Amiga Halfbrite mode

Extra Half Brite, is a planar display mode of the Amiga computer.
This mode uses six bit planes. The first five bit planes index 32 colors selected from a 12-bit color space of 4096 possible colors. If the bit on the sixth bit plane is set, the display hardware halves the brightness of the corresponding color component. This way 64 simultaneous colors are possible while using only 32 color registers. The number of color registers is a hardware limitation of pre-AGA chipsets in Amiga computers.
Some contemporary games and animations use EHB mode as a hardware-assisted means to display shadows or silhouettes. EHB is often used as general-purpose 64 color mode with its own restrictions.
Some early versions of the first Amiga, the Amiga 1000, sold in the United States, lack the EHB video mode, which is present in all later Amiga models.