https://developers.weixin.qq.com/minigame/dev/guide/

示例代码中封装的绘制矩形的函数，在执行前会清空整个屏幕，从而导致后面代码中下方的飞机被清除。

const { windowWidth, windowHeight } = wx.getSystemInfoSync()
function drawRect(x, y) {
  context.clearRect(0, 0, windowWidth, windowHeight)
  context.fillRect(x, y, 100, 100)
}

我改成了这样，仅供参考：

const { windowWidth, windowHeight } = wx.getSystemInfoSync()

function drawRect(x, y) {

//context.clearRect(0, 0, windowWidth, windowHeight)

context.clearRect(rectX, 0, 100, 100 + rectY)

context.fillRect(x, y, 100, 100)

}