i guess so - A total middle finger to whatever you're talking about. You'

A total middle finger to whatever you're talking about. You're saying 'go ahead, I don’t care, do your stupid thing.'

'You're gonna eat that whole cake?' 'I guess so.' (He was already eating it.)

'You’re leaving me hanging?' 'I guess so.' (He was already gone.)

'You’re gonna fail the test?' 'I guess so.' (He was already asleep in class.)