px units used

To be truly device independent this should abandon most `px` measurement units and embrace `em`, `rem` and viewport units.

It would be nice to use `flexbox` for the services, although potentially impractical.

Start by inspecting the site's HTML and stylesheets and searching for the existing px measurements. Determine which measurements should use em, rem, or viewport units, and clarify whether the optional flexbox idea is in scope; done means the agreed layout is device-independent without unintended visual changes.

索引モデルが issue の本文から書いたものです。