Thank you for playing my game and for your comments. Regarding the corals, they are multiple on the map (random number, depending on the level you are at, but you can only use them once.
But it's true that I decided to make the game easier, I wanted someone to be able to play and see all the levels and the last boss in 5-10 minutes. The reasons for this is that I assumed that most people will not allow much more than 10 minutes for each game they rate.
If I would do tha game again, I thing I would change the 3rd level to make it as a "boss". So the game would be 2 levels, 1 boss, 2 levels, 1 boss. making the game more dynamic.