You can do a lot in a browser these days. Including, under Edge for Windows 10 Mobile, running Progressive Web Applications, which have access to most of a smartphone's features. Here, Level PWA is a two-axis spirit level with loads of data - perfect for those ad-hoc DIY jobs when you never seem to have a level around when you need it...

From the (super short) Appscope listing:

A spirit level in web app form.

The URL to tap on or type in is spiritlevel.app .

Of course, you can turn this into an 'app' yourself with PAWA or just pin it 'as is' on your Start screen. Or just add it as a 'Favourite'. It's up to you. If you're confused by the different PWA options then check out my feature here.

Here's level PWA in action:

It's remarkably accurate - who'd have thought we'd be running utilities like these in a browser window one day? Note that the 'Clear' control toggles to a 'Zero' one and can be used if, for any reason, you need to recalibrate the level from a known surface or if your phone sensors are slightly 'out'. Unlikely, but worth knowing there's a way to reset things!