It's basic manners to give your all to a game that someone made with their whole heart, you know? Hitting the pause button would be rude to the game!
Literal
With-all-one's-might made-[passive] game [on-には], with-all-one's-might tackle [nominalizer-の] [subject-が] manners is [explanation-なんだよ]? Pause-button [emphatic-なんて] push-[if-たら] game [to-に] rude is-[もん].
一生懸命 ('with all one's might') is an extremely common adverb/phrase — literally 'one lifetime, one fate,' derived from the older 一所懸命 ('stake your life on one place'). The sentence repeats it twice for parallel structure, first as 'made wholeheartedly,' then as 'tackle wholeheartedly.' ポーズボタン is the loan 'pause button.' なんて dismissively flags the action. 失礼 ('rude, impolite') is used as a predicate adjective. The sentence-final もん adds childlike emphasis — 'because, see!'