Serious product recommendation: the Franklin Sensors iLevel. It's so obvious and useful in the week I've had it while hanging picture frames that I wonder why no one made this years ago. The "green" level is accurate to within less than 0.4º, better than a normal bubble level visually

https://www.youtube.com/watch?v=21stnmNfka8

Franklin Sensors iLevel Official Video

YouTube
@mathowie Second recommendation I've seen for this in a week.
@mathowie And it gets bonus points for a clever product name
@mathowie The video shows everything level, but how do the lights indicate which side needs to be raised or lowered? That’s intuitive with a bubble.