Platformer Movement Code

/// @desc Movement

// Input

keyboard_set_map(ord("W"), vk_up);
keyboard_set_map(ord("A"), vk_left);
keyboard_set_map(ord("D"), vk_right);

var _right = keyboard_check(vk_right);
var _left = keyboard_check(vk_left);

key_jump += buffer * keyboard_check_pressed(vk_up);
if key_jump > 0 key_jump--;

var _move = _right - _left;
vel.x = lerp(vel.x, _move * spd, _move != 0 ? acc : dec);

if vel.y < 10 vel.y += grav;

if place_meeting(x, y + 1, obj_wall)
{
    if key_jump > 0
    {
        vel.y = sign(key_jump) * -jspd;
        key_jump = 0;
    }
}

// Collisions

if place_meeting(x + vel.x, y, obj_wall)
{
    while !place_meeting(x+sign(vel.x),y, obj_wall)
    {
        x += sign(vel.x);
    }
    vel.x = 0;
}
x += vel.x;

if place_meeting(x, y + vel.y, obj_wall)
{
    while !place_meeting(x, y + sign(vel.y), obj_wall)
    {
        y += sign(vel.y);
    }
    vel.y = 0;
}
y += vel.y;