ratio   = radius / (wreck1.radius - radius)
        shiftx  = (x - wreck1.x) * ratio
        shifty  = (y - wreck1.y) * ratio
        slope   = (wreck2.x - wreck1.x) / (wreck1.y - wreck2.y)
        Yfunct  = lambda fx: slope * (fx - x) + y
        place   = y - wreck1.y - slope * x

        A = 1 + slope ** 2
        B = 2 * slope * place - 2 * wreck1.x
        C = slope ** 2 + wreck1.x ** 2 - wreck1.radius ** 2

        p3x =  ( (- B) + (B ** 2 - 4 * A * C) ** (1/2) ) / (2 * A)
        p4x =  ( (- B) - (B ** 2 - 4 * A * C) ** (1/2) ) / (2 * A)

        self.p1 = (x - shiftx, y - shifty)
        self.p2 = (x + shiftx, y + shifty)
        self.p3 = (p3x, Yfunct(p3x))
        self.p4 = (p4x, Yfunct(p4x))