Complex sentence: Highly reflective flat screens tend to suffer from hot spots, when part of the screen seems much more bright than the rest: this is a result of the high directionality (mirror-likeness) of such screens.
Split into simpler sentences: Highly reflective flat screens tend to suffer from hot spots, when part of the screen seems much more bright than the rest. This is a result of the high directionality (mirror-likeness) of such screens.