function _init()
    -- initialize

    -- enemy
    e = {}
    e.f = 1
    e.x = 0
    e.y = 0
    -- player
    p = {}
    p.found = false
    p.distance_b = 0
    p.f = 2
    p.x = 118
    p.y = 118

    -- columns
    bb = {}
    b1 = {}
    b1.f = 3
    b1.x = 40
    b1.y = 40
    b2 = {}
    b2.f = 3
    b2.x = 80
    b2.y = 80
    add(bb, b1)
    add(bb, b2)
end

function object_collide_with(x1, y1, x2, y2, gx, gy)
	-- checks if an object has collided 
	-- with another object, then calculated
	-- the angle between the ball and the other object

    -- gx = gravity horizontal center
    -- gy = gravity vertical center

    if (gx == nil) gx = 4  -- 8x8 --> 8/2 
    if (gy == nil) gy = 4

	--local bump = c1 and c2 and c3 and c4
	local distance = sqrt(((x2+gx)-(x1+gx))^2 + ((y2+gy)-(y1+gy))^2)
    local angle = atan2((x1 + gx) - (x2 + gx), (y1 + gy) - (y2 + gy))
	local direction = flr(angle * 8)
	return distance, angle, direction
end

function player_collide_with(x, y, w, h)
	-- checks if the player has collided 
	-- with another object, then calculated
	-- the angle between the ball and the other object

	return object_collide_with(p.x, p.y, x, y, w, h)
end

function distance_between(x1, y1, x2, y2)
	-- calculates the distance between two points

	return sqrt((x2-x1)^2 + (y2-y1)^2)
end

function check_player()
    if (btn(0)) p.x -= 1
    if (btn(1)) p.x += 1
    if (btn(2)) p.y -= 1
    if (btn(3)) p.y += 1
end

function _update()
    check_player()
    p.found = false
    local distance, angle, direction
    -- check the distance from the target
    distance, angle, direction = player_collide_with(e.x, e.y)    
    for i, b in pairs(bb) do
        local distance_b, angle_b, direction_b = object_collide_with(b.x, b.y, e.x, e.y)        
        if distance_b <= 10 and abs(angle-angle_b) < 1/6 then
            angle_b += 3.1415/240
            e.x = b.x - cos(angle_b) * distance_b
            e.y = b.y - sin(angle_b) * distance_b            
            p.found = true
            break            
        end
    end
    if not p.found then
        e.x += cos(angle) 
        e.y += sin(angle)
    end    
    if distance_between(e.x, e.y, p.x, p.y) < 8 then
        -- reset if the enemy touches the player
        e.x = 0
        e.y = 0
    end
end

function _draw() 
    cls(0)
    for i, b in pairs(bb) do
        spr(b.f, b.x, b.y)
    end
    spr(p.f, p.x, p.y)
    spr(e.f, e.x, e.y)
end