GameMaker Knockback Direction Broken?

[_Proxy]

I'm trying to knock back my player in the opposite direction he shoots his gun. But it only seems to be working on vertical directions...

PLAYER CREATE EVENT

hspd = 0;
vspd = 0;
hspd_force = 0;
vspd_force = 0;
force_applied = 0;
force_dir = undefined;
spd = 2;

PLAYER STEP EVENT

// Inputs
var down_key = keyboard_check(bind_down);
var right_key = keyboard_check(bind_right);
var left_key = keyboard_check(bind_left);
var up_key = keyboard_check(bind_up);
// Input Change
x_input = right_key - left_key;
y_input = down_key - up_key;

if (x_input != 0) or (y_input != 0)
{
    len = spd;
    if (hspd != 0) { image_xscale = sign(hspd); }
    sprite_index = spr_player_run;
}
else
{
    var len = 0;
    sprite_index = spr_player;   
}

// Force
if (force_applied > 0)
{
    hspd_force = lengthdir_x(force_applied, force_dir);
    vspd_force = lengthdir_y(force_applied, force_dir);
    force_applied *= 0.9;
}
// Movement
dir = point_direction(0, 0, x_input, y_input);
hspd = lengthdir_x(len, dir) + hspd_force;
vspd = lengthdir_y(len, dir) + vspd_force;
// Collisions
if (place_meeting(x + hspd, y, obj_collidable))
{
    while (!place_meeting(x + sign(hspd), y, obj_collidable))
    {
        x += sign(hspd);   
    }
    hspd = 0;
}
if (place_meeting(x, y + vspd, obj_collidable))
{
    while (!place_meeting(x, y + sign(vspd), obj_collidable))
    {
        y += sign(vspd);   
    }
    vspd = 0;   
}
// Application of movement
x += hspd;
y += vspd;

GUN STEP EVENT

var dir = point_direction(x, y, mouse_x, mouse_y);
// Origin
x = holder.x - lengthdir_x(current_recoil, dir);
y = (holder.y - 9) - lengthdir_y(current_recoil, dir);
// Rotation
image_angle = dir;
// Flipping
if (dir > 90) and (dir < 270) { image_yscale = -1; } else { image_yscale = 1; }

// Cooldown counter
if (cooldown_counter_start)
{
    cooldown_counter++;
}
// Shooting
if (mouse_check_button(bind_shoot)) && (ammo != 0)
{
    // Cooldown check
    cooldown_counter_start = true;
    if (cooldown_counter >= cooldown_time) or (first_shot)
    {
        // Audio
        audio_play_sound(snd_shoot, 10, 0);
        // Bullet
        var buffer_x = lengthdir_x(bullet_buffer, dir);
        var buffer_y = lengthdir_y(bullet_buffer, dir);
        var inst = instance_create_layer(x + buffer_x, y + buffer_y, "Instances", obj_bullet);
        inst.direction = dir;
        inst.direction += random_range(-bullet_spread, bullet_spread + 1);
        inst.image_angle = inst.direction;
        inst.speed = bullet_speed;
        
        // Ammo and recoil
        ammo--;
        current_recoil = recoil;
        
        // Variables
        cooldown_counter = 0;
        cooldown_counter_start = false;
        first_shot = false;
        
        with (obj_player)
        {
            var dir = inst.direction;
            force_dir = -dir;
            force_applied = 4;
        }
    }
}   

// Calculate Recoil
current_recoil = max(0, floor(current_recoil * 0.8));

 

[_Proxy]

SOLVED!
Thanks to a user on the PixelatedPope's Discord: @Sahaun#1172
all i had to do was make the horizontal direction inverse

Instead of

hspd = lengthdir_x(len, dir) + hspd_force;
vspd = lengthdir_y(len, dir) + vspd_force;

in the player's step event

I should have done:

hspd = lengthdir_x(len, dir) - hspd_force;
vspd = lengthdir_y(len, dir) + vspd_force;