This is a really lovely game with simple nice-looking 2D graphics and catchy music. I enjoyed challenges it gave me especially in last 2-3 levels and the ending was adorable. The only elements I feel to suggest to make it even more interesting is adding new levels, maybe even power-ups to help the duck during the most challenging tasks for example endurance to spikes for 5-7 seconds and/or giving the duck possibility to make higher jumps if catching a specific power-up that is time-constrained (i.e. 10-15 seconds). Even adding secret levels, a plot behind the duck's task that may explain the ending (maybe it's just symbolic of reaching someone's heart by finding the key to make the relationship blossom) and medals might make the game even more enjoyable. As last thing I would suggest to add a button before running the game that tells the player which commands to use (WASD or arrow keys for movements and spacebar for jumping) even if the mechanics of the game are simple to be easily grasped.
Besides these suggestions I liked the game a lot and it has the potential to become something really interesting. I liked chiptunes during levels, they really have a nice upbeat vibe^^
Welcome to NG and keep it up!