Achieving Rank S on Hard mode isn't really that hard to do. It just has to do with understanding the game a little bit and investing consitently into RP and haste. However, this guide tries to limit the number of playthroughs you will need to do in order to get all 10 achievements for this game. At minimum, you will be required to do a total number of 3 playthroughs:

• Normal Mode for S Rank
  
• Misc. Achievements on Normal Mode
  
• Hard Mode for S Rank

Note: The instructions for normal mode and hard mode are identical.

I encourage trying to beat S rank on Normal Mode first. This way, if you are not yet fully comfortable with the game (or make some bad upgrade decisions), you can potentially use that save to unlock the Misc. Achievements.

As mentioned previously, achieving S rank is not that difficult. As long as you consistently buy RP potions ("Potions of Freshness") and the haste potions to clear floors more quickly, you should be good. In order to achieve S Rank, you must clear B99F by day 85. The two times I cleared S Rank, I cleared on day 81 (which can actually be quite a bit of extra time).

Keep in mind that for achieving S rank you CANNOT die due to the 85 day time restriction. (This will also let you get the achievement "Who do you think you're messin' with?"). Achieving S Rank on Hard mode is identical to achieving S Rank on Normal Mode (and completing hard mode will not give you the achievement for normal mode - so no double dipping unfortunately).

Early Game:

The beginning can be the most frustrating part in order to get right. Here is the build I used to consistently beat the first boss on B9F:

• Damage
  
• RP
  
• HP Recovery
  
• HP Max
  
• Attack Speed
  
• RP
  
• Damage
  
• Accuracy

Tips for Remainder of Game:

• Always buy RP as your first upgrade after defeating a boss.
  
• Buy AT LEAST 1 RP upgrade every 10 floors
  
• Buy 1 haste upgrade each 10 floors (a good rule of thumb is to look at the day vs. your current floor. Your current floor should be greater than or equal to your day. If it's lagging behind, invest in a haste upgrade to catch up. You will get a huge burst of money and haste later in the game to propel far ahead to meet the 85 day deadline).
  
• Max HP is not as important as you think (until the late game). Be very stingy with these upgrades; HP recovery is far more important.
  
• Keep Max HP under 10,000 until you beat Floor 50BF in order to get an achievement.

Milestone: Floor B50F

It is important that you get enough damage in to clear the boss at Floor B50F. Usually, I have around these upgrades each time I reach that floor and clear with ease:

• Damage Alpha: 7
  
• Damage Beta: 2
  
• Attack Speed: 7
  
• Chaos: 2

Late Game:

By Floor B70F, it's hitting crunch time. Make sure to save in case something goes wrong. Keep investing in RP as before, and absolutely make sure that you have a Level 3 "Potion of Chaos" before you hit the boss on B89F. Make sure you heavily, heavily invest in HP restoration and Max HP. Enemies on B90F and up will be unable to be killed without dealing large amounts of damage to you before you kill them. Between Floor B90F and B99F, Max out HP Restoration before you start pushing your remaining money into Haste potions.

The rest of the achievements you will need after clearing S Rank should be completed on Normal mode. The following requirements for achievements should be left:

• Get to B50F with less than 200,000 Max RP
  
• Take an attack from the boss on B50F
  
• Take an attack from the boss on B99F

There's a chance that you've played a good deal of the game already and have been killed by the boss on B50F already. If so, the other two achievements should be that much easier.

B50F:

For these first two achievements, get to B50F without getting above 200,000 Max RP. This should be simple enough. However, invest more money into health, and invest very little into damage. This should be done to ensure that you get destroyed by the boss on B50F. Keep in mind that the boss also takes double damage from the Potion of Chaos.

B99F:

In order to reach the last boss without killing it, I had the following upgrades by the time I faced the boss on B89F:

• Attack Alpha: 9
  
• Attack Beta: 8
  
• Attack Speed: 9
  
• Potion of Chaos: 3
  
• Potion of Void: 1

Then focusing on HP upgrades (do not buy anymore damage upgrades now) will allow you to clear up to floor B99F safely.

This is my first Steam guide, and I hope it helps anyone looking to fully complete this game.

Of course, let me know if there are any questions or if you have determined better methods, builds, or requirements at stages in the game.