平台游戏的屋顶碰撞问题

function movement(gravityMov, speedMov, jumpMov, canDoubleJump, canWallJump, canDash) {
    mask_index = Spr_duck;

    function checkWallSlide(canWallJump) {
        mask_index = Spr_wallJumpCol;
        if (OnGround == 0) {
            if (place_meeting(x, y, Obj_water) && canWallJump == 1) {
                canWallSlide = 1;
                sprite_index = Spr_duckHang;
                dashable = 1;
                Jumps = 1;
            } else {
                canWallSlide = 0;
                sprite_index = Spr_duck;
            }
        } else {
            canWallSlide = 0;
            sprite_index = Spr_duck;
        }
        mask_index = Spr_duck;
    }

    if (!(keyboard_check(ord("M")))) {
        JumpButtonPress = 0;
    }

    // 控制左到右
    if (keyboard_check(ord("A"))) {
        if (!(Velx < -2)) {
            Velx -= speedMov;
            DirFacing = -1;
        }
    }
    if (keyboard_check(ord("D"))) {
        if (!(Velx > 2)) {
            Velx += speedMov;
            DirFacing = 1;
        }
    }
    if (keyboard_check(ord("N")) && canDash == 1 && dashable > 0) {
        Velx += 10 * DirFacing;
        Vely = 0;
        dashable -= 1;
    }

    // 跳跃
    if (keyboard_check(ord("M"))) {
        checkWallSlide(canWallJump);
        if (canWallSlide == 1) {
            Vely = 0 - jumpMov;
            DirFacing = 0 - DirFacing;
            Velx = DirFacing * 4;
            JumpButtonPress = 1;
            canWallSlide = 0;
        } else {
            if (Jumps > 0) {
                if (JumpButtonPress == 0) {
                    Vely = 0 - jumpMov;
                    Jumps -= 1;
                    JumpButtonPress = 1;
                    if (OnGround == 0) {
                        Velx = 0;
                    }
                }
            }
        }
    }

    // 摩擦力
    if (Velx > -0.5 && Velx < 0.5) {
        Velx = 0;
    }
    if (Velx > 0.5) {
        Velx -= FrictionPower;
    }
    if (Velx < -0.5) {
        Velx += FrictionPower;
    }

    // 水平碰撞
    mask_index = Spr_duck;
    Pastx = x;
    x += Velx;
    if (place_meeting(x, y, Obj_water)) {
        y += 1;
        if (place_meeting(x, y, Obj_water)) {
            y -= 1;
            x = Pastx;
            Velx = 0;
        }
    }

    // 应用垂直运动
    mask_index = Spr_duck;
    Pasty = y;
    y += Vely;
    if (place_meeting(x, y, Obj_water)) {
        y = Pasty;
        y += 15;
        if (place_meeting(x, y, Obj_water)) {
            y = Pasty;
            Vely = 0;
            OnGround = 1;
            Jumps = canDoubleJump;
            dashable = 1;
        } else {
            Vely = 0;
            show_debug_message("TOUCHING ROOF");
        }
    } else {
        OnGround = 0;
        if (canWallSlide == 1) {
            Vely = 0;
        } else {
            Vely += gravityMov;
        }
    }

    image_xscale = 2 * DirFacing;
    checkWallSlide(canWallJump);

    // 其他碰撞
    mask_index = Spr_breadCol;
    if (place_meeting(x, y, Obj_duck)) {
        target = instance_position(x, y, Obj_duck);
        if (target != -4 && target.object_index == Obj_duck) {
            if (target.TouchingBread == 1) {
                instance_destroy();
            }
        }
    }
    target = instance_position(x, y, Obj_bread);
    if (target != -4) {
        if (target.object_index == Obj_bread) {
            instance_destroy(target);
            global.Bread += 1;
        }
    }

    image_xscale = 2 * DirFacing;
    checkWallSlide(canWallJump);
}