Nice idea, game-play lacks any depth though. first play through even though I didnt understand the threat I just kept all the babies in one corner and I won. next play through I even tried to lose to no avail until later I found out that the babies would leave through the door. None of that was ever explained anywhere.
After i got a hang of things i tried your endless mode and since there was no real goal or incentive to go further i told myself i would aim for 420, but i noticed at around 120 the babies started going really fast until they were practically just snapping into the door. it feels like you are using some sort of "x += (doorx - x) * time/200;" type thing for the movement, which feels very unnatural when they just start flying towards the door when i let go of them. the best way to increase difficulty is not to make things closer to impossible but instead add more depth and force more decisions on the player, example would maybe be some babies are slower but take longer to pick up so you have to decide which one to spend your time on, or maybe furniture and stuff acts like obstetrical so locations actually have a strategic advantage aside from simply distance to the door, maybe the babies have hunger or happiness and the more upset they get the more likely they are to try to escape so you should keep them near somewhere where you can feed them and make them happy but those areas are easy to escape from, or maybe they need both feeding and something else like entertainment and those are in different areas and you have to choose where to put the babies. these are all things that will add more depth to the game and overall more interest. as the time goes further things could change forcing different decisions like some furniture moving or changing or the player gaining/losing abilities. so many potential things you can do with this incase you plan on developing this further.
Overall i could definitely feel the love poured into this project and it was a cute and nice feeling experience to play, i really hope to see you develop this further and i will follow to see what you do with it. Congrats on submitting!