Your game is super adorable!
The idea behind it, you guys as a couple making the game, those sweet graphics and sounds - I love it all!
Although I admit, those constantly smiling faces that never change get creepy with time, some animations wouldn't hurt. The screen was a bit too narrow for me as well (someone else suggested this) and I had a hard time reacting to obstacles, had to redo lots of times (thank god you put in checkpoints!). The coins respawn whenever you respawn so you can pick them over and over again especially since some checkpoints had coins with hearts to collect nearby. And I didn't know I had to wait for the princess to come down from the castle so I kept walking forward and fell off and died! lol Maybe put something at the end to stop this from happening? :P
All in all, I love the game, well done :D