I really loved the narrative of the game, and it was clear how much we cared for Hippo. It was easy to see the care our character had for him, and it made me determined to save him as well. My main critique is that it feels like your character isn't as dedicated to saving him as you would think, since they never intentionally look for something to save him in the different time periods. I think adding a line or two about how you're hoping the butterfly effect will save him could help this, or by adding in more exploration in the time periods (though that's beyond scope I'm sure.) The game was well written beyond a few grammar mistakes, and I was really invested in the story!