Unblock is a sliding puzzle set in a crowded parking lot. Cars and trucks are packed in tight, and your job is to shuffle them out of the way so the red car can drive out of the exit. There are 48 levels, from a couple of moves to over fifty.
The rules
The lot is 6 squares by 6. Cars are 2 squares long and trucks are 3.
Each vehicle slides only forward and back along its own lane, never sideways, and never through another vehicle.
The red car sits in the third row, which has an exit on the right. Slide it all the way to the exit and it drives out, clearing the level.
Moving vehicles
Drag a car or truck along its lane and it snaps to the nearest square when you let go. One slide is one move, however far the vehicle goes, and sliding the same vehicle again straight after still counts as one move.
On a computer you can also press Tab to pick a vehicle and the arrow keys to slide it. Undo takes back your last move, and Restart puts the lot back as it started.
Par and scoring
Every level has a par: the fewest moves it can be solved in, worked out by a computer solver. Levels are ordered by par, so they get steadily harder, from Easy through Medium and Hard to Expert.
You score 100 points for each par move, scaled down if you take more moves than par. Your best time and fewest moves are saved for every level, and levels you solve in par are marked in the Levels list.
Levels and progress
Clearing a level unlocks the next one.
Open Levels at any time to replay a level you have reached and try to beat your time or match par.
Leave mid-level and the lot is saved, so you can pick up where you left off.
Tips for harder lots
Work backward: find what blocks the red car, then what blocks that vehicle, and so on until you reach one that can move.
Trucks standing across the red car's row are usually the key. Look for a way to make room above or below them.
Sometimes you have to move a vehicle away from where you want it so that another one can get past first.
If you get tangled up, Undo a few moves or Restart. Short of par is impossible, but matching it is the real challenge.