Some fixes implemented :)

Hello everyone, here is a list of things I did while fixing the game:

- I managed to fix the issue with the background tiles after a bit of moving layers about and toggling the background transparency to Yes;

- edited the values for jumping and falling strength and gravity of the character's mask object (under the Platform behaviour) so that Metallen's jumps are less floaty and he falls down faster;

- made changes to Metallen's jumping so that the sound effect plays ONLY when he leaps into the air, and

- cropped the one-pixel tall line below the Ziggs' sprites which previously had them floating above the ground by the height of one pixel :)