Well done making your first game! I like the vibrant colours and straightforward theme - easy to pick up and play. I hope you had fun doing it. Maybe for your next project (I'm assuming you've got the game dev bug now!) think about adding the following:
1) a start screen showing the game title, with some simple instructions and a results screen so players know how well they've done - you can use new layouts in Construct to achieve this.
2) a score system - for example in this game you could have a timer - the faster you find the 3 castles the higher the score. That way players have an incentive to replay the game so they can try and beat their best time.
3) some sound effects - you can record these yourself using a microphone (it's fun doing it this way - I do it a lot! :)) or use a tool like "sfxr" which allows you to generate lots of different sounds with just the click of a button. I'm sure your parents will help you find this on the internet.
I look forward to seeing your future creations!