方便解释一下这段代码吗？

[ripperhe]

        //三角形两边的比例
        let scale = (lineLength - 2*margin)/(lineLength - lineWidth)
        for i in 0...3 {
            var keypath = "transform.translation.y"
            if i%2 == 1 {
                keypath = "transform.translation.x"
            }
            let lineAnimationTwo                   = CABasicAnimation.init(keyPath: keypath)
            lineAnimationTwo.beginTime             = CACurrentMediaTime() + duration/2
            lineAnimationTwo.duration              = duration/4
            lineAnimationTwo.fillMode              = kCAFillModeForwards
            lineAnimationTwo.isRemovedOnCompletion = false
            lineAnimationTwo.autoreverses          = true
            lineAnimationTwo.fromValue             = 0
            if i == 0 || i == 3 {
                lineAnimationTwo.toValue = lineLength/4 * scale
            }else {
                lineAnimationTwo.toValue = -lineLength/4 * scale
            }
            let lineLayer = lines[i]
            lineLayer.add(lineAnimationTwo, forKey: "lineAnimationThree")
        }

这段代码中 三角形两边比例指的是哪个三角形，没看太懂，能简单解释一下这个 scale的含义吗？

还有这个 lineLength/4 是从那里来的？

lineAnimationTwo.toValue = lineLength/4 * scale