但在中国，旅游的核心是“打卡”。
10 additional monthly gift articles to share
，推荐阅读下载安装 谷歌浏览器 开启极速安全的 上网之旅。获取更多信息
Visualizing quaternions by 3blue1brown A great intereactive introduction/refresher for quaternions. It focuses on intuition rather than mathematical definitions
The first calculation takes ~30 seconds while models download. Subsequent runs are fast.