Ah, the classic equation: CPU cooler with thermal paste not properly applied + tempered glass PC case = shattered dreams and glass everywhere.
The red circle is highlighting where someone forgot to remove the plastic cover from the thermal paste. That tiny mistake just cost them a $100+ case and hours of cleanup.
Nothing says "I'm having a productive day" quite like your PC literally falling to pieces because you rushed through step 3 of the assembly manual. The sound of tempered glass shattering is the universe's way of saying "maybe stick to console gaming."