Gridlock EscapeWorking backwards
Start where it ends.
Most solutions are easier to find from the finish than from the start. This guide plans two levels backwards and then plays them forward, move by move.
What the last position looks like
Trying moves from the start is slow, because most moves lead nowhere. The end is the one position you know exactly: every solution finishes with the hero sliding into the gap in the right-hand curb, and just before that slide every square between the hero and the curb is empty.
So the question is not “what should I move first?” It is “what has to be out of those squares, and what has to move for that to be possible?” You answer it one link at a time, and the first move of the solution is wherever the answers run out.
One level, from the exit
Level 18 has par 5. Here it is from the end backwards:
- The hero has to cross row 3, column 6. Truck C stands there, so C has to leave row 3.
- C is a truck, so its only way out is down, into rows 4 to 6 of column 6. Row 6 is empty. Row 4 holds truck F and row 5 holds car G, so F and G have to leave column 6.
- G has room: one square to the left frees column 6 in row 5.
- F is at the right-hand edge, so its only direction is left, by one square. That square, row 4 column 3, belongs to car D.
- D is free. It can go up one or two squares, or down two, and any of them empties the square F needs.
The chain ends at D, so D is the first move. Playing the plan forward, deepest link first, gives this:
Start 1. D slides 2 squares up 2. F slides 1 square left 3. G slides 1 square left 4. C slides 3 squares down 5. A, the hero, slides 1 square right and drives out
Solved in 5 moves. Par is 5.
G was free from the start, so it could have gone first, second or third. In all, level 18 has 28 different shortest solutions, and they share one shape: D before F, F and G before C, C before the hero. If you find that shape, you have found the solution, whichever order you play the free vehicles in.
Cross off the exit that cannot work
A car has two exits, and the wrong one can cost you a long detour. Level 26 shows how to rule one out before you touch anything.
The blocker is car E, in column 5. It could leave downward, but only by ending in rows 4 to 6, and there are just three squares there. Car G already occupies two of them and, being vertical, can never leave the column. E and G need four squares between them, so E can never go down. The exit is crossed off without a single move.
That leaves up: rows 1 and 2 of column 5. Row 1 holds car D, which has to slide left out of column 5, and it can only do that if row 1 is clear to its left. Car C is in that row, and to move left C needs column 1 free. Car B stands in column 1, and B can only get out of row 1 by going down, into the square where the hero is standing.
The chain, read from the end, is E, D, C, B and then the hero itself. Level 26 starts with the hero moving, one square to the right, to let B drop:
Start 1. A, the hero, slides 1 square right 2. B slides 1 square down 3. C slides 1 square left 4. D slides 2 squares left 5. E slides 1 square up 6. A, the hero, slides 3 squares right and drives out
Solved in 6 moves. Par is 6.
The hero moves twice in this solution. The first slide makes room, and the last one leaves. Nothing about the hero makes it special on the board: it is one more vehicle in the chain.
You cannot trap yourself
Every slide can be undone by sliding the vehicle back, because the squares it just crossed are still empty. So no position you can reach is a dead end. From anywhere on the board you can get back to the start, and from the start there is always a solution. A wrong turn costs moves, never the level.
That is why trying a plan is cheap. Make the first moves of the chain, and if it does not unwind the way you expected, undo and read the board again. What you learn from the failed attempt, such as a vehicle that turned out to be wedged, goes straight into the next one.