This guide is current as of February 13th, 2021 and covers all 12 chapters released at the time. If future updates change the levels or add new ones, please let me know in the comments.

This guide will discuss the ? level packs at the end of each chapter. These levels usually feature a unique gimmick, frequently in the form of a special mechanic, and often require you to think outside the box. Some of these can be quite obtuse or reliant on knowledge from outside the game. I hope this guide will be helpful if you find yourself stuck.

General Note: If you solve every level in a pack, but you don't get the star at the end, check back to the other levels. Some ? level packs have mechanics that influence previous levels or change win conditions on them. You only get the star if *all* puzzles of the pack are completed at the same time.

Rules
1. Start on a Circle.
2. End on a Square.
3. Exactly 1 Star.
4. No Triangles.

1-?-1 and 1-?-2 are straight-forward. Then the gimmick comes into play, which you might have already discovered accidentally.

Hint for the gimmick:
Experiment around until you break an implicit rule.

Explanation of the gimmick:
You are not constrained by the level boundaries. You can continue the line outside the grid on "invisible" tiles.

1-?-3 should be straight-forward now.
1-?-4 requires you to use the star on the far right to fulfill rule 3.

Rules
1. Start on a Circle.
2. End on a Square.
3. No Triangles.

2-?-1 and 2-?-2 are straight-forward. Then the gimmick comes into play.

Hint for the gimmick:
The puzzles are connected, so check back and forth.

Explanation of the gimmick:
The square tile you end on will have a circle on the next puzzle. The circle (and thus your starting tile) only spawns when the tile is empty (not already used by a square or a triangle)

Approaching it logically you can now work backwards from 2-?-5. Since the top center is occupied you have to end on the bottom center of 2-?-4, and so on. Until you realize that you have to start 2-?-1 by disregarding the hint and finshing on the bottom left square instead.

Rules
1. Start on a Circle.
2. End on a Square.
3. No shapes inbetween start and end.
4. Only one type of shape per area.
5. Exactly 2 shapes per area.

3-?-1 already makes the gimmick obvious.

Explanation of the gimmick:
All shapes will be pushed around by your line until they hit a wall. You can only enter your final square if it is backed up against a wall.

All that is left is to figure out a path that fulfills all the rules.

Sample Level Solutions:

3-?-2 (above)

3-?-3 (above)

3-?-4 (above)

3-?-5 (above)

3-?-6 (above)

3-?-7 (above)

Rules
1. Start on a Circle.
2. End on a Square.
3. No Triangles.
4. Gimmick.

Hints for the gimmick:
1. Go back to 4-?-1 after trying 4-?-2.
2. You can use right-click to clear a puzzle.

Explanation of the gimmick:
Rule 4: Your line must cover the same tiles on all puzzles.
Your starting and end points will be different, but you have to end up with the same shape covered.


Helpful image if you know the rules but struggle with the execution (above).


Solution (above).

Rules
1. Start on a Circle.
2. End on a Circle.
3. All tiles with little squares.
4. Gimmick.

Hints for the gimmick:
1. Note the positions of the circles.
2. Observe the square tiles as you draw on the first 3 levels.
3. On the 4th level go back and compare the earlier levels.

Explanation of the gimmick:
Rule 4: Enter and exit all square tiles in the same cardinal direction as you've started and ended the corresponding level.
The number of small squares on a tile indicates which puzzle in this pack it corresponds to. You have to enter and exit the tile in the same directions as the circles are on which you have started and ended the corresponding puzzle. If you started 5-?-1 by drawing a straight line from left circle to right circle, then all 1-square tiles need to be entered from the left and exited through the right


Sample full solution (above; click image to expand). Warning: Spoils the whole level pack.

Rules
1. Start on a Circle.
2. End on a Square.
3. All Stars.
4. No Triangles.

Hint for the gimmick:
1. If you get stuck, check out the other puzzles in the pack.
2. 6-?-4 is the most useful to understanding the gimmick.

Explanation of the gimmick:
Everything is horizontally mirrored around the center line of 6-?-4. If you draw on 6-?-1 you are actually collecting shapes on a horizontally mirrored version of 6-?-7. Puzzle 2 corresponds to puzzle 6, 3 to 5. Puzzle 4 is in itself mirrored.

Rules
1. Start on a Circle.
2. End on a Square.
3. Make it to the end having collected all Triangles.

Explanation of the gimmick:
After passing over a triangle, every subsequent move (regardless of its direction) will slide the whole puzzle 1 tile into the cardinal direction that the triangle is pointing at.

Hint for 7-?-5:
You are bumping against the edge of what you can see. How can you force the game to show you more?

Solution for 7-?-5:
Switch to windowed mode (middle button in the top-right). Then adjust the height of the window until it is relatively short, but very wide. You should now have enough space to solve the puzzle.

Rules
1. Spell the name of the puzzle game that the level is referencing.

Note: Do not feel bad for using the solutions below, this is a challenge unlike any other in the game. It requires cultural knowledge from outside the game. If you happen to not be aware of the games in question you have virtually no chance to solve some of these puzzles, so don't feel bad for using this guide. Before playing this, I had never heard of one of the games.

Solutions:
8-?-1 "Understand", the game you are playing.
8-?-2 "The Witness" as indicated by the verious shapes, which play a prominent role in that game.
8-?-3 "Baba is You" as indicated by the characters and flag.
8-?-4 "FEZ" as indicated by the main character.
8-?-5 "Portal" as indicated by the portals and the companion cube symbol. If you are stuck: You have to use the portals at the far ends of the puzzles to teleport from T to A.

Rules
1. All Circles.
2. No Squares.

Hint for the gimmick:
Listen closely. How can you use the different audio cues to speed up blindly using brute force?

"Explanation" of the gimmick:
I'm drawing a bit of a blank here myself. The symbols obviously fade out, but I have not found a logical pattern from which to infer their loction on the last two puzzles. I think you are supposed to use brute force aided by the audio cues. At least that's what I did. If you click single tiles it will only play the "no rules correct" sound effect if you've hit a square, which makes it fairly easy to determine their locations. The circles are harder. If you mark a known square and then a bunch of other tiles you will only get the "some rules correct" sound effect if you've marked *all* circles, which can help exclude areas. But ultimately it comes down to brute force, just with a minor speed increase.
If you have a more stringent explanation, please let me know in the comments.


Solution for 9-?-4 (above) Everything that is not (audibly) a Square seems to be a Circle.


Solution for 9-?-5 (above) You can easily figure out the grid of Squares but which nook to start and end in and which path around the center to take I had to brute force.

Rules
1. Gimmick.

Hint for the gimmick:
Don't force yourself to solve it in one go. Getting frustrated with the complete lack of information actually helped me find the solution. I left and returned a couple of times and then it clicked.

Explanation of the gimmick:
Rule 1: Reproduce the shape of the levels on the level select screen that match the color / chapter number of the rule dot.
You can start and end on any tile you want and the final shape can be anywhere on the 7x7 board.


Solution (above; click image to expand) Well, the reference image at least so you don't have to constantly start over after returning to the menu.

1. Gimmick.

Hint for the gimmick:
1. Pay attention to the grid sizes on the individual puzzles. They are important.
2. If you are still stuck, skip to the last two puzzles and experiment there until you notice something odd.
3. Or maybe return later in an hour or two with a fresh perspective.

Explanation of the gimmick:
Rule 1: The number of tiles marked spells out the current date and time set on your computer in the format: century, decade and year, month, day, hour, minute, second.

Sample Level Solutions:
If it currently is February10th 2021 at 1:20 and 17s the puzzle solutions would be 20-21-2-10-1-20-17. Given the last puzzle is the a seconds counter, the solution will be ever changing. Thankfully you can mark a future minute value, then switch to the last puzzle. Once the minute changes and 1 second passes you can simply mark down 1 tile which will also re-evaluate the minute counter and mark the puzzle completed. Having the system clock popped out into a separate window helped me watch the seconds closely.

Some Notes on Limitations:
If you ever open the level again, you will have to enter new values. And it appears that some values are simply impossible to input. You can't put down a zero and an empty grid will never validate even if you solve the remaining puzzles while its values is zero. Also, you can't enter a 31st day on a 5x6 grid. It seems like sometimes you might be forced to wait (or manipulate your system clock).

Rules
1. Fill all tiles.
2. Follow the path (fixed corners, variable lengths).

Explanation of the gimmick:
The first puzzle sets the path for all the others, meaning the challenge is figuring out a path that works for all board configurations (landscape, portrait, even and odd rows/columns). The previoius levels in the pack should have made this clear already, but do note that you can follow the same path in very different configurations since you can adjust the length of the segments.


Sample solution to the gimmick (above).


Full solution (above; click image to expand). Warning: Spoils the whole level pack.


And that's it for all the ? level packs. I hope you've found this guide useful.