the cackling began normally , then ascended louder , and louderand then the tension that polluted the room slowly began to clear as the two had almost embedded themselves in their peculiar amusement feeling their own cheek muscles ache from boasting too much uncontrolled laughter , losing the feeling in their legs , having to bend their knees , throwing their heads down , laughing like two friends that had pulled off an incredibly-risky , death-defying prank and were now venting in joyous celebration .