Nabucodonosor
Squire
Just using a shovel is considered 'being efficient'? Also, with other achievements likes this (Tiki-taka from soccer event) you can get more than only the bronze achievement.
5 tiles with one shovel is, of course, maximum: gold -- so there's no blue badge for the every-day-shovel.I suspect to get the achievement you have to clear 5 tiles.
It's worse with "sandblaster" 'cause is' maxxed out at silver with 7 sand tiles because with current game rules it's impossible to blast 8 or even 9 sand tiles which, I assume, would bring gold and blue badges. Why introduce those achievements if you can't actually achieve half of them? That has to be a (brain) bug. ^^