added go to play market button
added shield
added shueld health
added shield health bar
some fix
added test level
fix use shield)
added shield like another unit
fix one bug
all unit: added shield like another unit
change design in about screen
added shuied hp to magazine)
added gc
fix level bug size
added fog texture
added fog to screen; fix bug with zIndex unit
added cool fog manager
added fog movent; change simple bullet size; fix bullet destroy out of screen scaled;
added fog like wave object