Route Digger is a dig-and-guide puzzle: you carve away earth with a drag of the mouse, and gravity carries a ball down whatever channel you've made toward the goal.
It looks free-form but isn't — dig too much and the ball falls straight past the target, so the interesting problem is digging the minimum needed rather than the maximum you can.
Digging as little as possible. Removing too much earth takes away the walls that steer the ball, so the ball falls straight past the goal.
Many levels place stars along optional routes, which need a more careful dig than simply reaching the goal.
Yes — drag to dig. Nothing to install.