level curve

You might have a good game, with smart mechanics, smooth graphics, and a well pitched level curve, but the addition of freemium can pollute that.

Down a long slope, up a sudden rise, over a level curve where a fox-squirrel leaped into the road and scampered along it; up again, down into a hollow, across the ridge beyond—so he was going, when voices sounded again, then hoofs and wheels, and flashing and darkling in the woodland's afternoon shadows came a party of four, two under hats, two under bonnets, drawn by Bulger's handsome trotters in Garnet's carryall.