1e is a three-point perspective: the camera is turned against all three axes, so each set of parallel grid lines runs to its own vanishing point. 2b and 2c keep that camera with only two planes. 2a takes the room from 1c and puts it behind a flat page, as a one-point perspective that moves with scroll.
The page content stays flat, parallel to the screen. Behind it, floor slabs and walls sit in their own space. Scrolling lowers the eye through that space, so each slab is seen from above, then edge-on as it passes eye level, then from below. Scroll inside the frame.
A vertical plane and a horizontal plane crossing through each other at right angles. Same camera as 1e: the cursor moves it around the crossing.
Two vertical planes crossing at right angles, an X in plan. Both stand upright, so their vertical grid lines share one vanishing point while the horizontal lines run to two others.
The only element is the grid from dot_pattern_2.svg: 3px #444 dots on a 20px square pitch. Each plane is a patch of that grid placed in 3D. Planes are told apart only by the direction their grid runs and by hiding the dots behind them. Hover each artboard.
Six faces of one cube, each a square patch of the grid. Faces on the far side are hidden. Move the cursor to turn it.
One sheet folded into eight panels. Moving the cursor left to right deepens the folds, and each panel hides part of the one behind it.
Floor, walls and ceiling of a room with three freestanding panels inside. The cursor moves the eye, so the panels cover and uncover different parts of the room.
A 5 × 5 field of square columns. Columns near the cursor rise in whole grid steps and hide the ones behind them.
Three planes crossing at right angles through one point. The cursor orbits the camera around them, and each plane hides the parts of the others behind it.
Four plates stacked one cell apart, so the top plate covers most of the others. Moving the cursor up spreads them, and left or right slides them out of line.