I just looked through your code and found the =+ instead of +=. But I was too slow to tell you. Another thing is, that the potions can not spawn at the top, but at the bottom, because you divide the width and height by 10 and multiply it by a number from 1 to 10. Either you should do it 1 to 9 or 0 to 10. I will try getting a better score tomorrow, already too late now. ;)

The creating of the world happens immediately here instead of taking time based on the width and height when open it in Greenfoot. But here, it seems to produce some errors. The screen is shaking in a big world.... Does not effect the result, but it looks ugly.

Maybe the only end is the death :D Why does it shaking? You can only see new comments when refreshing the page. Just noticed it, too.

The update did not prevent the screen from shaking but the other problems were solved. Not in the first try, but in the second. First time after the update I still could not click the scoreboard because the game paused itself. Now it seem to work and I even see the instructions. Now I only need to find a way to not kill the samurais but all the others. ;)

I just killed like hundreds of enemies, but after killing the second samurai, there was that "A winner is you - You killed 20 Enemies" and the scoreboard again without getting a new highscore. Clicking the scoreboard did not do anything. What am I doing wrong? Isn't the goal of the game to survive by killing the enemies or what do I have to do?