Interlaced Flexible Line Interpretation.
Commodore 64 software display mode that uses interlacing. The Big Idea behind this mode is that the interlaced images use slightly different colors - and when images are changed 30 times per second, we... used... to... have... 16... colors... but --- now we have 128 different colors! =)
Of course, since the screen refresh rate is half of the normal, the picture flickers a bit...