OmegaAxel, it would literally take about 5 minutes to add a badge for beating elite, but having to beat the same game 3 times with the only difference being fewer grenades just didn't strike me as a compelling task. I can always add it in later if there's a demand for it.
For those having trouble with aiming, try using the keyboard (up and down arrows, plus space). There will be a marker on the ground showing where the boulder will land. Lead your targets a bit, as there's a bit of a delay with the boulder firing and landing.
Please note that due to performance issues, the hard badge has been changed from level 34 on medium to level 24 on hard mode. Sorry about any inconvenience!