add new npc
Gordon freeman
Alien slave( new effect)
HEV
scientists(hurt)
guard(hurt)
worker(hurt)
Black ops (have skill)
Hecu elite
Old versions were deleted by my friends, so I re-fixed them, added new effects, new skills

add new npc:

jump pad

snark mine

manta jet

○ When you stand on the jump pad, you will be bounced up

○snark mine can be set by the player after the door, when the enemy is close, it will explode and spawn 4 snark

○ manta landed alien guards near the enemy，only once