These are three-dimensional yajilin puzzles. In each puzzle, the four squares depict the layers of a $4\times4\times4$ cube.
- Shade some cells on each layer. The numbered cells show how many shaded cells (not includong numbered cells) are in the direction of the arrow.
- Some numbers have been replaced with question marks to make the puzzle more difficult. Cells with question marks behave the same as other numbered cells.
- Diagonal arrows point to squares on other layers. An up-left arrow points to smaller-numbered layers, and a down-right arrow points at higher-numbered layers. For example, a down-right arrow on layer 2 points to cells in the same row and same column on layers 3 and 4.
- Shaded cells cannot be adjacent to another shaded cell (even those on different levels). The shaded cells are allowed to touch the numbered cells, however.
- Unshaded unnumbered cells on each layer are all adjacent to one another in 2D (i.e. each layer is treated separately).
- Make a single loop in 3D space which goes through every unshaded, unnumbered cell.
This is a pencil-and-paper-games full solution... yay