Marsh/Row 4

Localization: between two doors, below Row 3.

Design: This row has the same colors than the rows 1 and 2, but it contains puzzles with new polyomino shapes (well actually, we should not call them polyomino anymore because of this). Most of these new shapes could not stand by themselves, as there would be no solution to the puzzle: with the 3x3 square where the central block is missing, it would not be possible to draw the line around the central block. For the two-blocks-in-diagonal shapes in the second puzzle, you would need to pass twice at the same point, which is forbidden in puzzles. Same thing for the variant in the third puzzle of the row. Only the double-2x1 piece in the last puzzle of the row could be drawn alone, although 1) it would make two regions and would thus not be recognized as matching the symbol, and 2) It is not possible to place this two-part polyomino in a way that covers its symbol.

Heuristic learned: So, the principle of these puzzles is that we should first try to combine these strange polyominoes with others to make a shape that can be traced in a puzzle. (This is different than the puzzles in the previous row where you would ask yourself where to place the polyominoes in the puzzle: here you first need to consider how to assemble the polyominoes before placing them in the puzzle.) More precisely, a good method is to identify in a polyomino the squares that are missing to make the polyomino's contour drawable in a puzzle, and then find how the other polyominoes in the puzzle can be used to fill these holes. That understanding will be very useful later for the blue-outline polyominoes, which require the use of similar strategies.

Unanswered question: A curious thing about this row is that it is between two doors. Doors would not be necessary if the designers' goal was just to force us into doing the rows of puzzles one after another: for that purpose it would be sufficient to connect the rows with wires so that you can only start a row after the previous row has been completed. Another reason to use doors could be to prevent us from seeing what happens next, or to prevent us from reaching a point where we can activate something. Clearly it is not the first case, since they made the structure upstairs (with Row 3), from which we have a nice view on what will come next. The reason might be to prevent us from reaching the other moving platforms, but in that case a single door would have been enough (and that would be useless since we can access these moving platforms by using the first shortcut door). So, why use two doors? Of course, we can invoke the general principle of Separation, but it may not be the only reason. Maybe it's related to how we solve the puzzles in that row, but it is not obvious. The strange piece in the last puzzle of the row, with it's two distant parts, could represent the two doors. As all puzzles in this row somehow require to pack polyominoes inside another polyomino, this could be a metaphor for packing puzzles between the two doors. Also, this is the first row of puzzles in the marsh that do not use obstacles (holes) in the grid, but doors are obstacles.

Relation with other puzzles: Row 2 can be seen in the background, above this row.