How to play
You are the lockmaster at Lock and Dam No. 19 in Keokuk, Iowa. Barges, towboats, pleasure craft and the Keokuk Belle queue up on both sides of the dam, and the only way past is through your chamber. Open a gate only when the water matches, shut both, then fill or drain the chamber to carry the boats up or down 38 feet. Every boat has a patience ring. Keep them moving, chain full lockages for a streak bonus, and don't let three boats give up and turn around.
Tap the two gate buttons and the fill and drain buttons. On a keyboard use A and D for the gates, W and S for fill and drain, Space for the next valve move. P pauses and M mutes.