You draw the road and a little truck drives it, but the ink still in the meter when you reach the flag is the score. So the honest ledge-to-ledge bridge is always the worst answer that works, and the game is twenty levels of finding the meanest line that still holds a truck up.
A gap, a flag on the far side, and a meter of ink. You draw whatever road you think will get a truck across, and then you are paid for the ink you did not use.
Ink drains by the length of the line, so the safe instinct - a broad solid bridge from one ledge to the other - works on the first few levels and is always the worst solution that works. A short ramp that flings the truck the rest of the way costs a fraction of it.
That turns every level into the same question asked differently: what is the least road this truck actually needs? Erasing refunds you in full, so the cost is only committed when you launch.
The truck has a motor, but it can only hold about a forty-five degree climb. Past that it stalls and slides back, which means a steep line is not a shortcut - it is a wall.
Downhill the same rule pays you. A drop drawn early buys speed you can spend on a jump later, and the cheapest crossings in the game are usually a short steep fall into a lip, with nothing at all drawn over the gap itself.
Ceilings force a low flat arc where you wanted a high one. Hazards make the direct line the wrong one. Later levels are built so the obvious bridge cannot be afforded at all, and the only routes that fit the meter are the ones that use the terrain.
Gold and silver thresholds are set from the best solution actually found for each level rather than guessed, so a gold is genuinely close to the tightest line available.