itch.io

Instructions need clarification? (Dragon isn't mentioned. Also, separating it into separate Text objects and sentences might help clarify it.) Mention that shooting rainbows at dragons freezes them for a second, for example. Can you kill the dragons? Not sure (but this can be clarified in extended directions.)

Also, instead of having the candy disappear when the unicorn flees (which is surprising and unexpected), what about losing all your candy (in addition to a health point) when you are hit by a dragon or its fire? (It would be like the dragon eating or burning up your candy.) 

Minor UI suggestions: make the text next to the coins and heart larger, color coded, and maybe place them both above the four keys, next to each other.

Since you've added multiple keys, you could make the levels more non-linear, and force the player to backtrack (obtaining one key is necessary to obtain another key located earlier in the level, for example).

More coins? The coin in the area with the flies at the beginning was fun because it was a challenge to collect. Maybe add more of those challenges, and then display the number of coins collected on the final screen. This adds replay value: players keep trying to collect more coins and get the highest possible score. 

Also, recommend a fancier "congratulations" message on the final screen (cooltext.com), and you could use the sparkle effect for "fireworks" -- every 1/2 second, for example, spawn a randomly colored sparkle at a random location on the screen. That could be cool :)

Increase the difficulty -- spawn more rain clouds! And to make the rain clouds more challenging, what about adding sine-like movement vertically in addition to the straight-line bullet movement?

Maybe change the firing controls, like in the spell shooter game, click the mouse and then shoot the fire in the direction of the mouse.

For aesthetics, maybe add a value-based animation to the colored raindrops -- Sine behavior, set to change Size (Magnitude 10, Period 2, for example).

Maybe when the game is over, add a "final score" to measure your performance -- the amount of fuel plus the amount of seconds, perhaps? That would motivate the player to be fast and precise when playing, and gives the game a competitive feel (who can get the highest score?).

Maybe display an immediate "game over" message if you run out of ammo and there are still leprechauns left, and add a button that appears that offers you the chance to try again.

Add some scenery elements to the area to make it look more interested. Maybe a grassy background, and bushes and trees?