And before start game you might know about these key in game
you have to hold down the button or if you just press it.it won't work if you just press it
and why i plan to use a key like this for quick change when the enemies is get nearby and you still doing another action and game over that why i prefer to code the control like this

control
use arrow key to walk
hold a to punch (+ 15 score)
hold s to kick (+15 score)
hold d to shoot (+10 score)
hold 2 while shooting to change the gun
hold e to use knife(+ 10 score)
hold w to use vaccine(+10 score)
hold q to set up the bomb (while stand in front of building)
that all i have to say.