on damage:
	attacker is holding sword
	if attacker has gray bye:
	loop all player
    level of loop-player is more than -1
        level of loop-player is less than 20
        if loop-player is sneaking:
            the block below loop-player is not air
            add 0.5 to level progress of loop-player
        add 0.3 to level progress of loop-player