function enemy_move_and_collide()
{
	var _y_spd_total = (y_spd + y_spd_kb) * global.time_scale;
	var _x_spd_total = (x_spd + x_spd_kb) * global.time_scale;
	
    if place_meeting(x, y + _y_spd_total, oParentSolid)
    {
        while !place_meeting(x, y + sign(_y_spd_total), oParentSolid)
            y += sign(_y_spd_total);
			
        _y_spd_total = 0;
		y_spd = 0;
		y_spd_kb = 0;
    }
    y += _y_spd_total;

    if place_meeting(x + _x_spd_total, y, oParentSolid)
    {
        while !place_meeting(x + sign(_x_spd_total), y, oParentSolid)
            x += sign(_x_spd_total);
			
        _x_spd_total = 0;
		x_spd = 0;
		x_spd_kb = 0;
    }
    x += _x_spd_total;
}

function enemy_check_hitstun()
{
	if hitstun_timer > 0
	{
		hitstun_timer -= global.time_scale;
		x_spd_kb = lerp(x_spd_kb, 0, 0.2);
		y_spd_kb = lerp(y_spd_kb, 0, 0.2);
	
		x_spd = 0;
		y_spd = 0;
		
		image_blend = c_orange;
	}
	else
	{
		x_spd_kb = 0;
		y_spd_kb = 0;
		
		image_blend = c_white;
	}
}

function enemy_get_hit(_damage, _kb_x, _kb_y)
{
    hp -= _damage;
    
    hitstun_timer = hitstun_max;

    x_spd_kb = _kb_x * kb_factor;
	y_spd_kb = _kb_y * kb_factor;

    if hp <= 0
	{
        is_dead = true;
        instance_destroy();
    }
}

/// @desc 优雅地以该实例为原点，给定宽高、偏移与持续时间为参数，生成敌人碰撞箱
/// @param {real} _x 碰撞箱宽度
/// @param {real} _y 碰撞箱高度
/// @param {real} _x_offset 碰撞箱与该实例在x轴上的偏移量，默认为0
/// @param {real} _y_offset 碰撞箱与该实例在y轴上的偏移量，默认为0
/// @param {real} _duration 碰撞箱持续时间，默认为0，即无限
function enemy_create_hitbox(_x, _y,
_x_offset = 0, _y_offset = 0, _duration = 0)
{
	var _hb = icd(oEnemyHitbox, x + _x_offset, y + _y_offset);
	_hb.owner = id;
	_hb.sprite_index = sEnemyHitboxRec;
	_hb.x_offset = _x_offset;
	_hb.y_offset = _y_offset;
	
	var _base = 2;
	_hb.image_xscale = _x / _base;
	_hb.image_yscale = _y / _base;
/*
oEnemyHitbox的基础大小为2*2
因为gml的1*1sprite无法将重心放在middle/center
此处定义后续用于缩放
*/	
	if _duration != 0
	{
		_hb.persist = false;
		_hb.duration = _duration;
	}
	return _hb;
}