Block Shadows▶Play

The blocks are glued face to face, so some of them can hang out over empty space. Their colour tells you how high they are: teal blocks sit on the floor, gold blocks are on the second layer and coral blocks on the third. Because of that, every face you can see belongs to exactly one place in the room, and the game only shows objects whose shadow you can work out from what is visible.

The lamp always shines straight across. When it hangs above the room, the shadow falls on the floor and covers every square that has a block anywhere above it. When it stands at the front left, the shadow falls on the back right wall; at the front right, it falls on the back left wall. A wall shadow covers a square whenever any block lies on the straight line from the lamp to that square.

A run is 20 questions in four stages of five. Stage 1 lights the floor from above in a 3×3 room with 4 to 6 blocks and gives you 12 seconds. Stage 2 lights a wall from the side with 5 to 8 blocks and 15 seconds; from its third question the room is four squares wide. Stage 3 turns the puzzle round: two shadows are already painted on the room and you choose which of four objects casts both of them, with 18 seconds. In the first two questions the shadows are on the floor and one wall, after that on both walls. Stage 4 shows a curved arrow: picture the object turned 90° that way, then pick the shadow it casts on the lit wall, again with 18 seconds.

A right answer is worth 40 points plus up to 60 more for speed, shrinking evenly to nothing as the time runs out. A wrong answer costs 40 points and running out of time scores 0. After each answer the true shadow is painted onto the room, and in stage 4 the blocks turn so you can see why. Scores are kept to a hundredth of a point and the total never shows below zero.

Tips & strategy

From above, height does not matter at all. A column of three blocks and a single floor block make exactly the same square of shadow, so ignore the gold and coral blocks for a moment and just ask which floor squares have something standing on them, or hanging over them. Two of the four options are usually mirror images of each other, the same shape flipped across the line from the back corner to the front corner. To tell them apart, pick one lopsided feature, such as the arm that sticks out furthest, and check which wall it points toward in the room.

For a wall shadow, imagine sliding every block straight toward the lit wall until it touches. How far back a block sits makes no difference, only how high it is and how far along the wall. This is where the colours pay off: a coral block always puts shadow in the top row, a gold one in the middle row, and a gap under an overhanging block can stay lit if nothing else stands on that line. Read the shadow from the floor up, one row at a time, and the distractors usually fall away in the first or second row.

In the reverse stage the four objects differ by only one or two blocks, so you do not need to work out every shadow in full. Compare the options with each other first, find the block where they disagree, and then ask whether that block, or the gap where it is missing, changes one of the two painted shadows. Usually a single square of one shadow settles it.

For the quarter turn, do not try to rotate the whole object in your head. Follow one distinctive block, such as the only coral one or the end of the longest arm, work out where it ends up after 90° the way the arrow goes, and see which end of the lit wall its shadow lands on. That one square rules out half the options. Remember too that a correct answer is always worth at least 40 points while a wrong one costs 40: if you are down to two choices as the bar runs out, a guess breaks even, but with four left you are better off letting the time expire.