Example

var spd = argument0
var rof = argument1
var up = keyboard_check(ord('W'))
var down = keyboard_check(ord('S'))
var left = keyboard_check(ord('A'))
var right = keyboard_check(ord('D'))
var fire = mouse_check_button(mb_left)
var acc = argument2
var dmg = argument3
var run = keyboard_check(vk_shift)
var reload = keyboard_check_pressed(ord('R'))
var debug = keyboard_check_pressed(ord('P'))

if(debug){state = "class"}
//shooting
if(fire && alarm[0] <= 0 && ammo > 0 && !reloading){
    var acc_ = irandom_range(-acc, acc)
    var bullet = instance_create(self.x + lengthdir_x(self.sprite_width/2 + 8, self.image_angle + acc_),self.y + lengthdir_y(self.sprite_width/2 + 8, self.image_angle + acc_),obj_bullet);
    bullet.direction = self.image_angle + acc_
    bullet.dmg = dmg
    audio_play_sound(snd_gunfire,0,0)
    alarm[0] = rof
    effect_create_above(ef_smokeup,self.x + lengthdir_x(self.sprite_width/2 + 4, self.image_angle),self.y + lengthdir_y(self.sprite_width/2 + 4, self.image_angle),.005,c_gray)
    self.ammo--
}
if(!self.reloading && reload){
    alarm[1] = room_speed
    self.reloading = true
}

//x or y axis
if(run && self.sprint >= 0){
    if((left && up) || (left && down) || (right && down) || (right && up)){
        self.hspeed = (-left + right) * (spd/2) * sqrt(2) * 2;
        self.vspeed = (-up + down) * (spd/2) * sqrt(2) * 2;
    }else{
        self.hspeed = (-left + right) * spd * 2;
        self.vspeed = (-up + down) * spd * 2;
    }
    self.sprint-=2
}else{
    if((left && up) || (left && down) || (right && down) || (right && up)){
        self.hspeed = (-left + right) * (spd/2) * sqrt(2);
        self.vspeed = (-up + down) * (spd/2) * sqrt(2);
    }else{
        self.hspeed = (-left + right) * spd;
        self.vspeed = (-up + down) * spd;
    }
}
if(!run) self.sprint ++

//Horizontal collision
if (place_meeting(self.x+self.hspeed,self.y,obj_wall_parent))
{
    while(!place_meeting(self.x+sign(self.hspeed),self.y,obj_wall_parent))
    {
        self.x += sign(self.hspeed);
    }
    self.hspeed = 0;
}
//Vertical
if (place_meeting(self.x,self.y+self.vspeed,obj_wall_parent))
{
    while(!place_meeting(self.x,self.y+sign(self.vspeed),obj_wall_parent))
    {
        self.y += sign(self.vspeed);
    }
    self.vspeed = 0;
}