pickups should no longer spawn inside of obstacles
added a score
added the mushroom tileset. Had to update tileset a bit to make them work
increased grass friction a little
bush was too big, now smaller. Also mushroom background darker so that it is a different colour to the bush
fixed a bug where ladybugs would always oscillate around y=0 instead of their starting y. Also the medusahead script allows the magnitude of the oscillation to be changed. Increased this to 2 for ladybugs