How exactly does the P potion work?

The brewing manual's description for the P potion is awfully vague:

The P potion is a strange one. You cannot predict what it is going to do. It could heal you or damage you, make you stronger or weaker, or even turn you into someone (something?) else.

From this, I gather that the effects of the potion are random. But what possible effects are there, exactly? What can you do to influence the randomness?

The full logic of the P potion's effects is pretty complex. For starters:

• If you are a turtle, drinking a P potion will cause you to lose half your remaining health and then turn back into a human.
• If you have less than 8% of your health left, drinking a P potion will heal you for one of the following amounts, chosen at random: 3, 7, 10, 200, 400, 600, 50%, 65%, 80%. (EDIT: On closer inspection there's a bug here; if the game gives you a message saying you've healed 3 or 7 health, actually you've healed 10.)

Otherwise, the potion's effects are randomly determined based on the number of P potions you've drunk in the past--let's call this number P#. Here are the possible effects along with their chances of happening:

• There is approximately a one in (P# / 2) chance of either gaining or losing either 20% or 30% of your maximum health, determined at random. The first two times you drink a P potion this is guaranteed to happen (unless you are a turtle or have less than 8% of your health remaining), since it will be a one in one chance, or 100%. If you have drunk a lot of P potions this will become unlikely to happen, for example if you have drunk 10 potions your chances will be about 1 in 5 for this to happen (20%), for 40 potions it will be about 1 in 20 (5%), etc.

• If the above does not happen, there is approximately a one in (P# / 6) chance of getting one of four effects, chosen at random. Again, the more P potions you drink the less likely this is to happen, starting from 100% if you've drunk less than 6, and going down from there. Here are the possible effects:

  1. You will be unable to move for a short time.
  2. You will turn into a turtle for a short time.
  3. Your health will be completely restored.
  4. You will be reduced to 10 health.

• If neither of the above happens, the game will say "Something strange is happening." You will then cast a number of spells for free in quick succession. The spells you cast are (naturally) determined at random. There are three different possibilities:

  1. Acid rain, Teleport, Fireball
  2. Three Acid rains, followed by a Teleport
  3. Four fireballs intermixed with Teleports (so you will teleport between each Fireball)

The exact code that determines the P potion's effects can be found by downloading the game's JavaScript source code and doing a search for "castPlayerPPotion".