Celeste

The cassette to unlock these levels can be found in Chapter 4 after the first door that you need to flip the keys to open, and after that you can access them any time from the map. I recorded a quick walkthrough of both the cassette and the B-Side:


Timestamps are in the description, and I've also included a couple tips to make some of the moves make a bit more sense

Since this will be your first B-Side, I'll do some explaining
The B-Sides are unlocked after finding the cassette in the A-Side, or normal version, of their given level. So, for the B-Side of Chapter 4, near the very end of Section 1 you'll come to a room with very strong wind pushing you left and three clouds that lead up to the top-right corner of the zone. Jump to the second cloud and jump left instead of right to find a semi-hidden path. Exit left and cross through the seed room to come to the cassette room. After collecting the cassette and finishing the level, you'll get your rundown of strawberries collected and total deaths, plus the unlock for the B-Side.

B-Sides are more difficult version of the given chapter, with the same theme and mechanics of the level, just turned up to 11. The sections are roughly the same length as their A-Side counterparts as well. Every B-Side ends with an alternating pink and blue platforming section with their Crystal Heart at the very end. Plus, they have a bangin' alternate version of the level's theme song. That should be everything, so let's get into it. I'll break each section down into their own parts so they're easily identifiable.

Section One

• Jump into the first bubble and ride it up, then hold right to fall into the second one and ride it into the third bubble. Ride that one down-right, then dash up-right into the fourth bubble, which you'll ride into the fifth bubble. Ride that one up-right through the gap, then fall between the two spiked walls and dash right for the last bubble, which you'll ride right, then dash up to the end of the zone.

• As the first platform starts coming towards you, jump for it and stick the landing. Jump over the first bramble and land back on the platform, then jump off of it and land on the lower platform ahead. Just before you meet your doom overhead, jump off and dash up-right to land on the right edge of the platform ahead. Jump over the bramble ahead and jump over the last one and dash up to reach the ledge overhead and exit right.

• Jump to the first bubble and ride it up past the brambles, grabbing onto the left wall. Climb up and jump over the walls ahead, holding right so that you can dash into the breakable wall and fall down to the bubble below. Ride it up and dash right through the gap and grab onto the right wall. Climb up and jump to the wall above, then transfer to the next wall, then into the bubble. Ride that up and grab onto the right wall, then jump left onto the closer wall and jump from there into the gap behind you to dash into the breakable wall below, grabbing onto the left wall after breaking it. Jump into the bubble that it was hiding and ride them to the right wall, where you can climb up and exit right.

• Use the jump pad and dash to get on top of the moving block and get ready for a lot of small guiding adjustments. Guide it down to fit through the first gap, then jump and dash over the wall to land back on it on the other side. Guide it down to avoid the incoming brambles, then guide it back up slightly to fit through the next wall. Jump over that one and repeat that again quickly for another small jump. Guide the block under the brambles, then guide it back up to fit through the next wall and jump over that wall, then quickly guide the block down to avoid the wall ahead. Guide it to fit through the next wall and wall bounce up to the bubble overhead, ride it up-right and fall to the next bubble, which you'll ride right and dash up-right to clear the brambles and land on the block far below. Guide the block a tiny amount up and dash up-left after you clear the wall and bounce off the wall overhead to reach the bubble, which you'll ride right and fall out of, then dash right after you clear the wall ahead to land back on the block below. Ride it to the end and exit right.

• Jump and dash to the moving block, grabbing onto it pretty low so you miss the brambles ahead. After you clear them, climb up and jump to the left wall, bounce off of it to reach the bubble and ride it right. Fall out of the bubble and fall through the brambles to dash right into two bubbles that catch you up to the block. Direct the second bubble up-right so that you can grab onto the block as you come out of it. Ride the block to the end and exit right into the next section.

Section Two

• Jump and dash to the first two crumbling platforms, then fall and dash right for the first bubble, which you'll ride up-right to land on the next crumbling platform. Jump and dash to the next bubble, which you'll ride up and dash as you come out to land on the crumbling platform overhead, then jump and dash to the end and exit right.

• Jump and dash to the crumbling platform, then jump and dash up to the wall overhead, which you'll jump off of into a bubble that you'll ride right and dash out of to reach a far wall that you'll grab onto. Slide down and jump left to reach the other wall, then slide down again and jump right to land on a crumbling platform in the void. Jump and dash up to the bubble overhead, which you'll ride up-left, then dash up-right for the last bubble. Ride it right and dash out of it to reach the end and exit through the ceiling.

• Use the binoculars if you like. Jump and grab onto the moving block to get started. Jump to the first wall and bounce off it to grab back onto the block, then jump to the jump pad on the right and bounce off the wall above to grab back onto the block again. Quickly jump to the right wall and bounce off of it to clear the block and grab the opposite wall, then jump to the left side of the moving block. In the next gap you'll need to jump over the wall and grab back onto the right side of it. Ride it into the next gap, then jump off and dash into the green gem, then up-left to the wall where you can jump to the end and exit through the ceiling.

• Climb up and look at the objective ahead. There are four blue gems to get here. As the moving jump pad is crossing to the right, jump and dash up-right to get the first gem and fall down to the second gem on top of the crumbling platform. Jump and dash to meet the jump pad, then fall down to the third gem below and dash up to meet the jump pad again. Hold left as the jump pad moves left to keep it beneath you, then fall down and dash into the bubble, riding it up-left to grab onto the wall and wait for the bubble to return. Jump and dash right to grab the last gem, then fall into the bubble and ride it right, then dash up-right to land on the jump pad and follow it right to be able to dash and land on top of the block that moved, then climb and exit through the ceiling.

• Jump and dash into the first bubble, which you'll ride up-right and dash right to land on one of the single crumbling platforms, then hop down them and jump and dash right to grab onto the low wall ahead. Climb it and jump and dash up to the bubble, which you'll ride right and dash out of it to land on the single crumbling platform far below. Jump and dash right to the bubble ahead, which you'll ride up and dash up out of while holding right to fall on the crumbling platform above. Jump left into the bubble, which you'll ride left, then dash up into the final bubble, which you'll ride right and dash out of to reach the end and exit right into the next section.

Section Three

• Jump and dash up for the first bubble, which you'll ride up-right and dash up as you come out to clear the wall. Hold right to clear the brambles below and land in the next bubble, which you'll ride down-right and immediately dash up-right for the next bubble. Ride that one up-left and hold right as you come out to grab onto the wall. Climb it and jump to the next wall ahead, then jump over the brambles and slide down the next two walls to get to the bottom. Jump off the wall and dash left to enter the next bubble, which you'll ride to the next bubble. Ride the second bubble right and dash up-right just before you would fall out of the bottom of the zone and die. Take this bubble up-right and hold right to clear all the brambles nearby, then dash up to reach the wall and climb up-right to exit right.

• As the first moving platform comes down, jump and dash onto it, then jump and dash to the next platform, quickly jumping again and dashing up to avoid the brambles below. Land back on the same platform, then jump ahead and land on the next platform. Wait for the platform to start moving up to jump off and delay your dash up so that the platform you're going to has time to return to you. As this platform moves up, jump out and dash up to land on it on the other side of the brambles, then as it starts moving down again you need to jump ahead and dash up-right to land on the last platform after it passes the brambles overhead. Jump to the end from there and exit right.

• Jump onto the moving block to get it moving. Jump and dash up-right to clear the first three sets of brambles that lead to the next moving block. Land on it as you jump over the third brambles, then immediately jump and dash up-right to land on the third moving block. Jump off this block and dash left as you fall through the gap ahead to grab onto the right side of the middle block as it comes through the brambles. Drop down to the bottom block and ride it past the next set of brambles, then jump out to the left and dash up-right to land on top of the middle block. Jump over the brambles ahead and land back on the same block, then crouch to clear the overhead brambles and ride this block to the end, then exit right.

• Jump and dash over the large block below to reach the cloud and use it to boost you up to the smaller block above. Grab onto it to get it moving, then drop to the large block below to get it moving too. Grab onto the left side of the block and ride it past the first wall. Guide it left as you rise to avoid the first set of brambles, then jump on top once the top of the block is clear to jump and grab onto the right side of the block and guide it right so that it can pass through the bramble-filled gap above. Jump onto the cloud and use it to boost you up and dash up-left to land on the left side of the block. Quickly jump to the cloud and use it to boost you up while holding left so you can wall bounce and reach the next cloud faster. Use that one to boost you up to grab onto the small moving block in the large block's path. Land back on the large block and ride it to the top, jumping and dashing to exit through the ceiling.

• Jump into the first bubble and ride it down-right, then immediately dash up-right into the next bubble. Ride it up-right and hold right to clear the brambles, then dash up-right into the next bubble, which you'll ride up and dash up-right out of to fall down the gap into the next bubble. Ride that one up and dash out of it to reach the wall above and jump off of it to reach the end and exit right into the next section.

Section Four

• The wind will change as you cross this zone. It's just jumping from one cloud to the next all the way to the end. The wind will start by blowing left. The wind will stop from the second cloud to the third. The wind will blow right from the third cloud to the fifth cloud. The wind will stop after the fifth cloud, then blow left just before the end of the zone. Exit right.

• Use the binoculars if you like. Jump and dash to the pink cloud and let it bounce you without jumping, then fall below the wall ahead and dash up-right to land on the next cloud. Don't jump again and hold right, then dash up-right between the brambles on the wall and ceiling to a third pink cloud. Jump off of this one and fall in the narrow gap between brambles, then dash right onto a fourth cloud. Jump and weave left to avoid the overhead brambles, then weave between the brambles as you fall down the narrow gap and dash right into a bubble, which you'll ride up-right to grab onto the wall and climb up. Jump to a fifth cloud, let it bounce you normally and dash to a sixth cloud. Repeat and dash to the final cloud, which you'll jump off of and hold right to fall down the staggered brambles to the exit.

• Get in the first bubble and ride it up, then dash up-right to get on the wall. Jump for the blue gem and fall back into the first bubble. Ride it right and dash into the second bubble, which you'll ride up-left to grab onto the wall. Climb it and jump right and dash up to get the second blue gem, then fall back down to the second bubble. Ride it right and dash and dash up to avoid the brambles and fall into the third bubble. Ride it right and dash up to grab onto the right wall overhead. Wall bounce up to the blue and green gems, then fall down and dash right into the fourth bubble. Ride it up-right and dash up for the blue gem, then fall down into the fifth bubble and ride it right. The wind will kick in, pushing you right so hold right and dash up-right to get the last blue gem and reach the now moving block and ride it to the end.

• The wind will be heavy to the right, so let it boost you as you jump and dash to the first bubble. Ride it down and dash right into the second bubble. Ride it up-right and dash up into the third bubble. Ride it up-right and let the wind take you to the other side of the brambles, then dash left into the fourth bubble. Ride it down-right and dash right for the fifth bubble. ride it up-left into the wall and grab on. Climb up and jump over the brambles ahead, then dash right into the sixth bubble. Ride it up and let the wind take you to the crumbling platform ahead. Jump off of it and ride the wind right, then dash up-right to reach the next crumbling platform. Jump to the next four crumbling platforms in a row, then jump and ride the wind right, then dash to the end, jumping quickly off the first wall if you need to grab onto it because it falls. Exit right.

• As the blue block is becomes usable, jump and dash onto it, then jump and dash to the next two blocks as they highlight. Jump and dash up to the pink block behind you, grabbing the green gem, then jump and dash right for the bubble ahead. Ride it right and dash for the small platform ahead. Wait for the pink block covering the heart to be highlighted for half of its time, then dash to the green gem ahead and fall down to dash into the heart and enjoy your achievement.

Timestamp: 1:03:12 & 1:14:58