Ruins
The Ruins is the first area and for the first few puzzles, Toriel will walk you through them. Here are the other solutions.
First Fall
Head down and then right into the next area. You'll walk across a dark patch of ground which will drop you into another room - continue through the door to the right to reappear on the other side of the dark patch in the previous room.
Slide Rock
A grey rock is in the middle of this room, push it to the grey square to dispell the spikes and continue.
Leaf Path
Now you'll come across a room full of the dark patches that let you fall through the floor. If you do so you'll come to a room full of leaves. Everywhere the leaves aren't is the path you need to take in the room above - go back through the door to come out at the previous room and take this path to move forward.
Three Rocks
The next room has three slideable rocks, one rock will need you to talk to it multiple times before it will go onto the grey panel and allow you passage past the spikes.
Six Falls
In the next room are six dark patches to fall through:
The top left will let you fight a Vegetoid.
The lower left patch will let you find a Faded Ribbon which gives you +3 to Defense.
Top middle has the switch you need to continue.
Bottom middle you can talk to Napstablook again.
Top right has nothing.
Bottom right has another Vegetoid.
Switch Perspective
Now we come to a bunch of pillars with switches. Try to make note of where the switches are located because the following sections are the same room on different angles which means the switches are hidden behind pillars.
You want to move through and find the blue switch which is behind the first pillar.
Now you can move past the spikes to the next room - in here you want the red switch which is visible next to the last pillar.
The final room wants you to hit the green switch behind the middle pillar.
Snowdin
Snowdin has many puzzles that the skeleton brothers have set for you - here's how to clear them.
Footsteps
Midway through you meet up with Papyrus and Sans again for more talk. Papyrus will end up walking over his trap to meet you leaving footprints behind, giving you a clear pathway to get to the other side unharmed.
Goal
This is an optional puzzle, where you can kick a snowball into a hole. Doing so quickly enough will earn you money, but it is not necessary.
Snow Map
There's a patch of snow-covered land here before some spikes. Pushing away the snow will reveal that there's a hidden switch back up north which you can return to and press to continue.
X's to O's
This time you'll come across a puzzle where you have to turn X's into O's. Step on the blue X's to change them, then step on the button above.
Then you'll meet back up with Papyrus and he will show you a more difficult X to O puzzle. You can exit or enter this puzzle at various locations, and X's will stay O's as long as you don't step on them twice making it a lot easier than it first appears. Here's one method, but there are many.
Next is a sliding puzzle.
For this one, start at the bottom and slide right across to the second X, then up, left, down, right, right, down, left, up, right, up, then onto the switch.
This will float you across a long bridge behind some trees. Once you're out the other side keep heading east - there is a southern path but you can't do anything with this just yet.
Waterfall
Waterfall introduces you to new kinds of puzzles.
Bridge Seeds
This section introduces a new puzzle with bridge seeds - you need to place them four in a row and they will form a bridge. The first puzzle is very simple:
The second puzzle is a bit tricker and requires you to build a vertical bridge, releasing the flowers from the end of the lowest sticking out point.
Telescope
The next area is full of echo flowers and wall signs with history written on them. You'll find a telescope near the middle of the room. Use it and look to the top left corner for a clue on how to get out of here.
Follow the telescope's advice and go up the northern corridor - inspect the wall to find a door.
Piano Puzzle
After you meet a large monster in a long corridor, keep heading east. When you come to another fork in the road ignore the northern route for now. Instead, if you continue east you'll come across a statue in the spotlight - ignore it for now too.
The next room has a bucket full of umbrellas, grab one and take it back to the statue.
The statue will begin to play some music, pay attention to the song. Head back to the fork in the road and take the northern route to find a piano in a room. If you're musically inclined you may be able to recreate the tune by ear, if not it's: open, up, right, open, down, open, down, right.
This will open a door, go through it to claim the orb. Unfortunately, you are apparently holding too many dogs to take the artefact. Open your inventory and dispose of the mysteriously appearing Annoying Dog who will absorb the orb and leave.
This gives you Dog Residue, which may sound like a lame reward but it's actually incredibly good. Using Dog Residue will fill your inventory with more of it plus Dog salad which is a healing item. This means as long as you keep one portion of it on you, you will always be able to heal.
Light Paths
You'll come to a dark area with skinny paths. You need to follow them and interact with the mushrooms to light up the next pathway. After the third mushroom, double back to continue on the path.
The next area is much the same but more difficult. Instead of mushrooms, there are lamps, and they only remain lit for a short amount of time. Try to head North East as much as possible in order to get out of this area.
Hotland
The Hotlands will have you following Alphy's advice for many puzzles - for the ones she doesn't help with here are the solutions.
Block Puzzles
These puzzles have you moving square blocks out of the way so you can shoot the opposing arrow. This puzzle gives you two bullets so you only need to move one block out of the way. Move the blocks down and push one to the side, shoot the block and use your second bullet to get the arrow.
Now make your way to the left building, Alphys will remove a pesky laser in your way to let you through.
This one is more complicated, shuffle the blocks up, left, down, and then fire through one block and once more to shoot the arrow. Now you can head back to the northern door and pass through, once you do so continue east until you find a dark room.
Switch Vents
After you cross through the barrier after only pushing two switches on fast-moving conveyor belt - you'll come to some launch pads.
This time they are accompanied by switches which will change the way many of the arrows point.
Use the first switch to go left then down, back up then back down, down, left, up, up, left to cross the puzzle - once you're clear continue west to find another save point.
More Block Puzzles
Another area where you can take launch pads to get to rooms with block puzzles. We are going to complete the southern puzzle first.
For this puzzle you only have one bullet, so you'll need to clear a path to shoot the other arrow. You'll want to put two of the blocks in the right spaces and the other two in the left space, then move the left space blocks only one to the left instead of all the way to the end to complete the puzzle. (Left, left, left, up, left, left, right, shoot.)
Now use the launch pads to go North to the next puzzle. This time you want to fill the left spaces and have one block on the right to clear a path.
The Core
For a large portion of this area Dr Alphys will be giving you some bad advice you have to follow.
Surviving Dr Alphys
You'll come to a point where you have to hit a switch to continue. Alphys will give you some bad advice about the orders the lasers will appear in. Instead, they'll be blue, blue, then orange, so stay still until the last laser.
Even though Alphys is making a lot of mistakes at the moment you need to keep following her directions regardless, so keep heading right. If you ignore her and go north at the cross roads you'll have to have another battle.
Next up is a path with more lasers. Dr Alphys will turn them off for you, but as you make your way across she'll call you again staying to stay still. The lasers will reappear and you'll have to move in intervals when they've turned off. They will flicker just before coming back on giving you plenty of time to stop.
New Home
The only real puzzle in New Home is finding the keys, it's not too hard but this is how it's done.
Inside you'll see a lock to stop you from going downstairs, interacting with it will tell you to go fetch the keys.
As you explore the house you will start to be interrupted by bits of story delivered in what look like random encounter fights.
The first key is in the kitchen to the left, the second is on a desk in the corridor to the right.
True Laboratory
This area is only available to those completing a full pacifist run. You will have to find several keys and use them in the correct locks to unlock a major door. You will also have to encounter monsters to get these keys.
This room has a save point, so do so as you will encounter enemies here. You can see a door with four colours on it - these are the colours of the keys you will need to find.
Keep reading all the notes and terminals you find and go left.
At the end of this room you'll find a set of 3 sinks, turn them all on and you'll start an encounter.
Memory Head
You'll need to 'Cell' each one to spare them. Dodge their attacks by moving quickly away from the white circles that appear. Ared key will appear in the sink when you're done - take the door next to the sinks and put the key in the box at the end.
Now go back to the save room and up through the nothern right-hand door. Keep heading right til you come to a room with some beds. The left-most bed in the center has the sheets pulled up. Check it to get the yellow key, take it and head through the northern door.
Start by heading right and you'll find a room with many fans and some smoke. At the far end of the room is a button, push it to clear the smoke. This will also trigger another encounter.
Amalgamate
Amalgamate is very similar to a previous battle. Choose, beckon, pet, play, pet, pet, to spare him.
Now head out of the room and head left til you come to a doorway north. Go through it and head straight up to the spooky curtain to get the green key.
Go left and you'll come to another room with a large skull and a save point.
Go through the door on the right of the skull to use the yellow key. You can also watch some videos which give more insight into the story on the tv here. Now Interact with the save point to find it's really another encounter.
Lemon Bread
You need to hum, flex, and unhug lemon bread to spare him, now keep heading on past to the left.
This room has some refrigerators and despite the suspicious nature of the one that is jumping around, it's the last one where you'll get another encounter.
Amalgamate 2
This time you'll need to 'joke' multiple times until you can spare her, then you can grab the blue key and head through the door to use the green one.
Backtrack to the room with the beds and save, just in case. Now go through the eastern corridor. As you pass the mirrors you'll have another encounter.
Reaper Bird
Pick on, Mystify, and Pray and Reaper Bird can be spared, then continue through the door to use the blue key.
Now you can make your way back to the room with the door with several locks and go through it. You'll find a room at the end with the elevator power control, use it to turn the power back on.
