Thank you for your helpful suggestions!
In fact I don't have enough time to complete the archery (in order to complete the multiplayer function), the game is a three-dimensional space, the operation needs to control the angle with the mouse, and the up and down movement controls the Z-axis (Like clip doll machine). Therefore, it is necessary to judge the Z-axis position of the arrow with a shadow.
I just updated the version on Github Pages, added shadows, and zoomed in on the characters. I hope you can think that archery has become reasonable!
Github Pages Version: https://johnsoncodehk.github.io/open-jam-2018/