Achievements

• Golden God - Unlock all bonus content (beating the games Coil, Aether, Time F**k, Triachnid, Spewer)
  
• Platinum God - 100% the basement colletion (Self-Explanatory)

Achievements for completing the chapters

• Forest Funk - Complete chapter one in Meat Boy
  
• Salty Dreams - Complete chapter two in Meat Boy
  
• Hells Bells! - Complete chapter three in Meat Boy
  
• Bonus Meat! - Complete bonus chapter in Meat Boy

You don't need to complete all levels of one chapter to complete it. Beating 3 levels of a level set (which has 5 levels each) will unlock the next level set.


Achievements for collecting the bandaids

• The Blue Castle Crasher! - Collect 4 bandaids in Meat Boy
  
• Dr. Fetus! - Collect 8 bandaids in Meat Boy
  
• Gish! - Collect 16 bandaids in Meat Boy
  
• <3 - 100% Meat Boy (collect all 24 bandaids)

There are 6 bandaids per chapter. The bandaid locations are written in this steamcommunity-guide by Steam-User Brosus:
Band-aid locations

The last bandaid (level 10 in bonus chapter 'expert') can be tricky. You mustn't fall under the bottom of the screen, so make a wall jump when you are landing on the assembly line. In this way you don't slip the line downwards.

Achievements:

• @ - Come full circle in Coil (You have to 'win' the game)

Winning the game will unlock the game "A.V.G.M." in the basement.

Video and Walkthrough Instructions by Youtube-User bewaretheb:

To bypass "non-level" screens - Rotate your cursor counter-clockwise.
You do not have to click or press any buttons, mouse movement is the only interaction with the game.

• 1st Level - Move your cursor left and right to make the sperm swim. Find an egg and then swim toward it, when you're close enough the sperm will automatically penetrate the outer membrane.
  
• 2nd Level - Separate the clusters by color. All of the circles are repelled by your cursor. When the red, blue, and green circles are all clustered together, while not touching any other color, the level will end automatically.
  
• 3rd Level - Rotate your cursor either clockwise or counter-clockwise to make your bubble spin in the respective direction. Avoid or roll off the obstacles coming up at you. The level will end when you get to the bottom.
  
• 4th Level - Guide the balls of food to your little embryo using the string. The brain sea-horse dudes will run-off with your food. Annoying, but food will keep dropping until you're done. Once you've eaten enough, the level will end.
  
• 5th Level - You control the top half of the screen with the bottom half of the screen. The pink kidney looking things on the lower half of the screen on the left and ride side make you rotate in the respective direction. The yellow intestine looking thing at the bottom propels you through the water. The vase looking, pink stomach thing sucks in food through the hole above your tentacles. Level ends when you eat enough food.
  
• 6th Level - Mouse over the other embryo jellyfish. The arrows fire automatically, just hold your cursor over the other guy. You will eventually catch up to them, and the level will end after contact has been maintained long enough.
  
• 7th Level - Think of your cursor as a counter-weight. You direct the movement of your jellyfish by balancing against gravity, or the momentum making you fall. Ultimately, you don't have to do really anything in this level it seems like. You can do nothing and the level will end automatically.

Achievements

• Lost - Complete Triachnid
  
• Found - Find and collect all the lost larva in Triachnid

self-explanatory

information by Steam-User twigx:
"For the "Found" achievment in Triachnid you can go to this website: https://www.chaptercheats.com/cheats/pc/110484/The-Basement-Collection-Cheats.htm
there are the locations of every larva (:"

I recommend the steamcommunity-guide Achievement Guide: Aether by Steam-User Cos

Achievements

• Oh, hello - Make progress through the main game in Time Fcuk (self-explanatory)
  
• Hey, do I know you? - Make more progress through the main game in Time Fcuk (self-explanatory)
  
• Why yes, you do actually - Make even more progress through the main game in Time Fcuk (self-explanatory)
  
• Sorry, i don't remember you - Complete the game the right way in Time Fcuk (beat the game the first time)
  
• How odd, because i'm very sure i remember you - Complete the game the wrong way in Time Fcuk
  
• Steven? - Create a level in the editor in Time Fcuk
  
• Please leave me alone - Complete chapter 2 in Time Fcuk
  
• I'll leave when you remember who i am - Complete the Unknown in Time Fcuk

-- more informations in progress --

Achievements

• Stomach Flu - Complete Spewer Chapter 1
  
• Bad Milk - Complete Spewer Chapter 2
  
• Hot Sauce - Complete Spewer Chapter 3
  
• Bile Butter - Complete Spewer Chapter 4
  
• Acid Reflux - Complete Spewer Chapter 5
  
• Spew Spew Spew - Complete Spewer Bonus Chapter
  
• Build it and they will Spew - Create and play a custom level in Spewer

Self-Explanatory.
I recommend the steamcommunity-guide Spewer Achievement Guide (In Progress) by Steam-User Ikuzen.

Completing Chapter 1-5 will unlock "Thicker than Water" (Comic by Edmund McMillen)

Achievements

• I - Get XXX points in one playthrough in Grey Matter (5 chains in one playthrough)
  
• II - Get XXXX points in one playthrough in Grey Matter (10 chains in one playthrough)
  
• III - Get XXXXX points in one playthrough in Grey Matter (20 chains in one playthrough)

The Descriptions of the achievements are misleading. You dont to collect 'points'. You got to get 5, 10, 20 chains in one playthrough.

• ( ) - Beat Mormal Mode in Grey Matter
  
• ( (o) ) - Beat Boss Rush in Grey Matter
  
• ( o ) - Beat Expert Mode in Grey Matter

Self-Explanatory.

This Game is unlocked by completing the game 'Coil'

I recommend the steamcommunity-guide A.V.G.M. Walkthrough/Achievement guide by Steam-User Salvatorum




???? achievements:
information by Steam-User JerryFilms:
"to get all 4 ??? achievements you have to complete all levels in A.V.G.M. it's recommended to get an autoclicker because in total you'll have to click about 150,000 times. 10k for level 1, 20k level 2, 40k level 3, and 80k level 4"

Not really a game. This contains random sketches and illustrations from 2004-2011. Its unlocked by beating "Time F**k" the first time.







But the bonus content of this leads you to the folder 'C:\Program Files\Steam\steamapps\common\basement\moregames' where you can find four swf-files --> Clubbe The Seal, Dumpling, Weltling, Weltling2. These are four additional flash-games which you can open and play with your web-browser (like chrome).

It's a comic by Edmund McMillen, which is unlocked by beating chapter 1-5 of Spewer.

information by Steam-User JerryFilms:
"to get all 4 ??? achievements you have to complete all levels in A.V.G.M. it's recommended to get an autoclicker because in total you'll have to click about 150,000 times. 10k for level 1, 20k level 2, 40k level 3, and 80k level 4"