Congrats on your first game ^_^
Suggestions: Add some music. You can find free, royalty-free music online to add to the game. You can also use any of the music in the audio portal here if you don't plan on making any revenue. The coin sound effect is just a little too high pitch (could just be me) but you can download audio software called Audacity (it is free) that will allow you to edit audio clips.
Also, there was no end game which was disappointing. Having just a simple 'Thanks for playing' would have sufficed after the player took the time to collect all of the coins.
Use the constructive criticism you get from feedback to improve your next project and keep making games :)