I strongly recommend that you only read as far as you've gotten in the game! Reading ahead won't help you at all and will spoil game mechanics. This game is much better when you get to discover things for yourself!

I'm creating this guide because it's a pain to backtrack into the hint levels while you're solving something. This contains all of the information from world-specific hints throughout the game as well as a couple other hints and tips. I hope that this makes solving easier for you!

• The demon can push blocks.
  
• Blocks have temperature (neutral, hot, and cold).
  
• When blocks of different temperatures touch, heat exchange occurs. After the heat exchange, all the involved blocks get the same tempearture depending on the amount of heat in the blocks. If there are more hot than cold, they become hot; if there are more cold than hot, they become cold; if there are the same number of hot and cold, they become neutral.
  
• You cannot move the demon or solve the level while the demon is hot.
  
• A level is solved when a turn ends with a solid block on the goal while the demon is not hot. When the levels are solved, the level blocks (often) change to another state (cold, movable, etc.).
  
• The body of the demon can transfer heat but cannot store heat. This means it isn't counted as a block when heat exchange occurs.
  
• Heat is not transferred to blocks whose sides are insulated. Insulation appears as a dark grey (white in dark theme) line on the side of the block.
  
• Blocks with fixing pins (dots in the corners) cannot be moved.
  
• Some blocks are partially insulated and can transfer heat only through certain sides.
  
• If the level edge is not insulated, blocks can exchange heat with the outside. The outside is infinitely large, so blocks will always take on the temperature of the outside.

• Blocks can have sticky sides. By default, sticky sides have no line on them.
  
• If a sticky side touches another block (or a level boundary), the two blocks fuse and become one rigid body.
  
• Sticky sides are never insulated.
  
• The demon does not stick to sticky sides.
  
• Glass (transparent) blocks, like the demon, can transfer heat but don't possess it.
  
• Glass blocks cannot be placed on the goal to solve a level.

• When you exit a level, the demon comes back out of the corresponding level block.
  
• Whenever you solve (or quit) a level, all levels are reset to their original states.
  
• The demon exits a level block from the same side it entered on.
  
• Once you have entered a level, any shortcuts to the level will activate. (For example, the [3-1] block above the entrance to w3 is a shortcut to the first level of the world. You can enter a level through a shortcut but will exit through the actual level block.
  
• When you enter a shortcut block, you will exit the actual level block from the side you most recently entered. For example, if in world 3 you enter [1] from the north, then enter the [3-1] shortcut from the west, you would exit the actual level block on the west.
  
• Level blocks in a world are numbered [1], [2], etc. Shortcuts (for World 3 in this example) are numbered [3-1], [3-2], etc.
  
• When you enter a level you're already in (for example, you enter 3-1 and then enter the [3-1] shortcut inside it), the level saves the current state as its "initial" state. If you then restart the level the blocks will return to that saved state. (You can solve or quit the level to reset it to the original state.)
  
• Heat does not transfer until you make your first move in a level.
  
• When the demon spawns in a space containing a block, the block is destroyed to make room.
  
• When you enter a level, the outside temperature is the same as the temperature of the block you entered. For example, if you enter a level through a cold block, the outside will be cold.
  
• When you exit a level, the outside temperature is always neutral.
  
• Level states are not reset until you solve/quit a level. For example, if you enter 3-11, then enter the [12] block inside, and then enter the [3-11] shortcut inside that, the state of 3-11 will be the same as when you left.
  
• The top left of the screen shows the path taken to get to the current level. For example, in 3-1 the path will show /w0/w3/1: you start in w0, then enter w3, and finally enter 3-1.
  
• If you "skip" parts of the path by taking a shortcut, you'll exit those levels on the same side you entered the shortcut. For example, in w3, there is a shortcut for 3-12 (the level block for 12 is inside 3-11). The path for the level is /w0/w3/11/12. If you enter [3-12] from the west, then quit to 3-11 and quit again to w3, you'll exit [11] from the west (even though you never entered [11] in the first place).
  
• When the demon is next to multiple levels, it will enter the level with the lowest number. Specifically, it will enter the block with the earliest world, then with the earliest level if there is a tie.

• Pistons have two states, extended (arrow pointing out) and contracted (arrow pointing in).
  
• Previously, each turn was a single "step" of making a move, then exchanging any heat if needed. Pistons allow multiple steps to occur during a turn.
  
• Each turn starts with the same move/transfer step as before. Then, if any pistons need to change and are able to do so, each piston makes a move and heat is exchanged after each move.
  
• Hot pistons want to expand. Cold pistons want to contract. Neutral pistons want to keep their current state.
  
• If a piston is extended and becomes cold, it will contract and become neutral. If a piston is contracted and becomes hot, it will expand and become neutral.
  
• If a piston wants to contract/expand and is unable, it will keep its temperature until it is able to do so.
  
• If an extended piston is pressed in, it will contract and become hot. (It will then try to extend again and become neutral, as above.)
  
• If a contracted piston is pulled out, it will expand and become cold. (It will then try to contract again and become neutral, as above.)
  
• The turn ends and the demon can move again once all pistons have moved (or tried to) and no heat needs to be transferred.
  
• As before, a level is still solved when a solid block is on the goal at the END of a turn. Note that this means if a block moves onto the goal and is pushed off before the turn ends, the level is not solved.
  
• The demon still becomes inactive when it gets hot. However, it is only inactive while it REMAINS hot. This means that even if the demon becomes hot during a turn, it can reactivate if a piston removes the heat source before the turn ends.

• When the demon enters a level from multiple directions, it also exits that level in multiple directions, with one demon coming out of each entrance side.
  
• Multiple demons will appear when a level has multiple spawn points.
  
• When a level has multiple demons, it can be solved as long as at least one of the demons is not hot.
  
• Remember that even if a demon becomes hot during a level, it can move again as soon as it isn't hot.
  
• When some demons enter a level, any remaining demons will stay in position outside (until you solve/quit the level, which resets the level state).
  
• When you solve a level, the only thing you can do is exit the level. For example, after a solving a level you can't undo to the solved state and then try to push the block off the goal.

• This world focuses on more complex piston setups. Note that:
  
  • The PISTON is the solid block with an arrow on it.
    
  • A piston has exactly one movable side.
    
  • Contracting the piston means pushing the movable side in.
    
  • Expanding the piston means pulling the movable side out (usually using a handle stuck to the movable side).
• A piston may contain exactly one block when contracted. When the piston is contracted, its arrow will be empty (meaning the piston chamber is empty) or filled (meaning there is a block inside).
  
• Note: You can mouse over a contracted piston to see the block (or space) inside.
  
• The interior walls of a piston are always insulated. Heat is never transferred a piston and its contents through the inside walls. (Heat can be transferred through the movable side though--see below.)
  
• Sticky sides do stick to the inside walls of a piston. (This can prevent the piston from expanding.)
  
• In order to push a block into a piston, there must be some immovable block supporting either the piston or the block. That is, a block will simply push the piston (or vice versa) unless there is something stopping the piston (or block) from moving.
  
• If the movable side of a piston is not insulated, it will allow heat transfer between the piston and the block touching that side. (This includes a block being pushed into an empty compressed piston, even though heat is not transferred through the other inside walls.)
  
• If a level block is placed inside a piston, it can only be entered through the face of the piston. The other three sides block access.
  
• You cannot push a piston from inside.
  
• Pistons can be made of glass. Remember that glass doesn't store heat, so a glass piston will immediately turn back to neutral when expanded or compressed (unless there is a cold/heat source touching it).

• This world focuses on "fourth temperature" (green) things (blocks or demons) which stay in place when resetting the level.
  
• Usually, resetting the level (i.e. pressing R) moves all things back to their initial state from when you most recently entered the level. Green things stay in place when resetting the level. (They return to their original positions when solving/quitting the level.)
  
• Green is "weaker" than hot or cold. This means that green can be transferred to neutral blocks, but green blocks will always become cold/hot when touching any cold/hot block.
  
• When a green thing is placed on the initial position of a non-green thing, resetting the level will destroy the thing because it can't move to its initial position. However, the level still "remembers" the thing and will respawn it as soon as the level is reset with its position open.
  
• From world 3, remember that entering a level again will set its current state as the "initial state" for resetting the level. Specifically, this means that if a block couldn't spawn because a green block was in its place, entering the level again will cause the level to "forget" it (because that block doesn't exist in the new initial state).
  
• Green blocks only keep their position when RESETTING the level. When (re-)entering or exiting a level, even green blocks will be destroyed by any spawning demons.
  
• You can still reset even if all demons are hot.

• When a move could cause multiple pistons to contract/extend, the one closest to the support contracts/expands. (From World 6, remember that either the piston or its block must be supported by an IMMOVABLE block in order to contract or extend. Extended pistons have a "springy" movable wall so they can't be used to support any pistons that come after.)
  
• When multiple pistons want to move at the same time, they move in their piston order (#1, #2, ...).
  
• Hint: You can press TAB to display/hide the piston order. When moving, you can also hold TAB to slow down each move/transfer to see why a piston is behaving the way it does.

• Things in a level have layers:
  
  • A thing outside of a piston is at layer 0.
    
  • A thing inside a piston is at layer 1.
    
  • A thing inside a piston inside a piston is at layer 2, and so on.
    
  • A thing gets deeper as it is contained by more pistons. Another way to think of it: the layer number of a thing is equal to the number of pistons it is inside.
• Remember from World 7 that if a green thing is in the position of a non-green thing while resetting, the non-green thing is destroyed. Now we have to consider both the space that it wants to return to AND its layer.
  
• When a non-green thing tries to return to a space with a green thing:
  
  • If the green thing is deeper than the non-green thing, the non-green thing is able to spawn "outside" it. For example, if a neutral piston contains a green block (layer 1) and a blue piston (layer 0) is trying to reset to that space, the green block will remain and the blue piston will contain it.
    
  • If a green contracted piston is shallower than the non-green thing, the non-green thing is able to spawn inside of it. For example, if a green contracted piston is in a space (layer 0) and a piston containing a neutral block (layer 1) is trying to reset to that space, the green piston will remain and the neutral block will spawn inside it.
    
  • If the green thing and the non-green thing are on the same layer, the non-green thing will be destroyed and "remembered" by the level. World 7 focused on this happening in layer 0 but it can happen in any layer. For example, if a piston contains a green block (layer 1) and a piston containing a neutral block (layer 1) is trying to reset to that space, the neutral block will be destroyed because the green block prevents it from spawning in layer 1.

World 0

• Remember from World 1 that a block can't be moved if it is pinned in place. World 0 is the first place where the level boundaries may not be pinned. This means exactly what you think it does: the level boundary can be pushed by the demon.
  
• Hint: The camera is fixed to the level boundary. So, if you push the level boundary left, all other blocks will appear to move to the right. Don't be confused when a pinned block "moves" this way!
  
• Pinned blocks can't be pushed into a piston.
  
• A pinned block in a piston is pinned to the piston. The piston can be moved around, but the pinned block can't be pulled out.
  
• You already know everything else required to clear World 0. Good luck!

• Every level can be completed. As the developer says in the hint for World 0: "If you find a level logically impossible, you have missed something." Sorry!
  
• Take a look at the Settings > Visual menu. You can change the grid style, toggle dark mode(!), and tweak the color for hot and cold blocks. You'll also unlock a few more settings as you progress; the game will let you know when you do.
  
• The sound design is very cool, but you can fully complete the main game without sound.
  
• Undo and redo are VERY helpful, but they aren't required to beat the game.
  
• It's possible to undo completing a level. Be careful not to go back too far!
  
• You don't have to beat every level to clear some worlds. (In fact, if you're clever you might find sequence breaks that let you access other worlds early.) Sometimes it's better to come back to a puzzle later instead of staring at it for another hour.
  
• Levels named after letters (such as 1-A) are extra levels. Even just reaching an extra level can be difficult. You'll often need to clear nearby normal levels in order to access an extra level. No extra levels are required to complete the main game.
  
• End game spoiler: Levels named after Greek letters (such as 0-α) are meta levels. You'll really need to break the world open just to reach these levels. In fact, you might not even notice one until after solving World 9. You don't HAVE to solve World 0 before trying for these, but you'll unlock some very helpful shortcuts and tricks toward the end of the main game to make it less painful.
  
• World A (wA) is an entirely separate world telling the story of the game's development. You can't use wA to advance in the main game. In fact, you can't enter until you're about to complete the main game, so don't worry about it until then!