child's play

From child + -’s + play, originally referring literally to play by a child.

• "Compared to my last job, this is child’s play."
• "The brawny craftsman finds it no child's play to mould his unpliant rugged masses; neither is guidance of men a dilettantism: what it becomes when treated as a dilettantism, we may see!"
• "In every county there were elderly gentlemen who had seen service which was no child's play."
• "He'd pull his bars apart like bow and bow-string, / And let them go and make them twang until / His hands had worn them smooth as any ox-bow. / And then he'd crow as if he thought that child's play— / The only fun he had."
• "I knew something of the railway engineer's uncanny genius for finding a path through such barriers if any path existed; yet I also knew the path would be no child's play."
• "It's just as quick out of the blocks. The five-car unit has three engines, giving it 2,820hp to play with, so the once-'feared' Devon banks of Hemerdon, Rattery and Dainton are child's play to these trains."

• kid stuff
• piece of cake

• easy as pie
• like taking candy from a baby
• easy