loading
https://pote-chil.com/html-maker/loading
html/css
https://gyazo.com/7b3d072c022d6f113b1cda9c5ce409b1 https://uxdesign.cc/loading-progress-indicators-ui-components-series-f4b1fc35339a
https://developer.apple.com/jp/design/human-interface-guidelines/progress-indicators
https://gyazo.com/2d33f423c965509e7ff82373248e2c85
HIG
https://developer.apple.com/jp/design/human-interface-guidelines/loading
HIG