I assume not many people have played the game due to it just showing an error if they don't have the latest java. There is likely a way to package a java application with an included runtime, or package it up with an installer for java.
The game itself was very confusing and I did not know what was happening at first, as the dragon teleports around, but I was able to beat it. Also, the background was blurry as it was a lower resolution than the sprites.
Keep making games. The more you make, the better you will get.