STICKMAN SHOOTING ZOMBIE SQUARES GAME. UPDATE PLAYER MOVEMENT WITH WASD IN MOVEPLAYER() FUNCTION. ZOMBIES DIE TO BULLETS. ZOMBIES SPAWN FAR AWAY AND MOVE VERY SLOWLY TOWARDS THE PLAYER. PLAYER DIES TO ZOMBIES. MOUSE IS USED TO AIM AND MOUSE LEFT CLICK TO SHOOT WITH AMMO. MOVEMENT WITH WASD KEYS. HIGHSCORE IS SAVED. ZOMBIES START VeRY SLOW AND UPGRADE AFTER EVERY 5 SCORE. UPGRADE PLAYER GUN TO 3 BULLET BLAST AFTER REACHING 10 SCORE. MAX ZOMBIES ON SCREEN IS 15 AT A TIME. ZOMBIES DROP AMMUNITION. without using document