armor penetration and movement speed

[quote=Yabuki]Hello, new to the game but not to the genre, i have a question on armor penetration and certain items that modify movement speed. 1. there are runes, items and a mastery (weapon expertise) that add X amount of AP percentage, and then there is a mastery called "sunder" that adds penetration points (2/4/6) now, the way i'm reading and understanding this, there is a base amount of armor penetration that a champion has, and it's % is increased. Then you have a mastery like sunder which increases this base, whatever it is. but i'm assuming this is not how it actually works, since it would be silly. But again, the wording leaves it open to interpretation. Can someone clarify on these two points? i'm also aware that armor reduction is different than armor penetration. 2. movement speed. I understand that boots add a value amount of speed, and items increase speed by a % but what about the item Trinity Force? All of the boots state "enhanced movement X", but TriForce says "12 movement speed" does this mean that it simply adds 12 points to the movement speed? Seems kind of silly when late game everyone is around 380-400 movement speed, 12 points ends up being like 3%? Again, i think there is a problem with wording. can someone clarify?[/quote]

[quote=Luther3000]There is no base amount of armour pen, percentage armour pen simply penetrates that percent of the target's armour. EG if target has 100 armour and you have the 10% armour pen mastery, you will damage them as if they had 90 armour. If you had [[Sunder]] too, it would act as if they had 100 - 6 = 94 - 9.4 for 83 armour, because flat armour penetration applies before percentage.[/quote]

[quote=Icuonuez]The way armor penetration works: Percentage is always applied last, if I'm not mistaken. In any case, they are both applied separately. Movement Speed: Nonboot-items give percentage movement speed. While [[Trinity Force]] might say 12 Movement Speed, it's really 12% increased movement speed.[/quote]

[quote=Luther3000]Yeah they should probably make that clear on [[Trinity Force]].[/quote]

[quote=Icuonuez][quote=Luther3000] Yeah they should probably make that clear on [[Trinity Force]]. [/quote] Agreed. Don't know why it has to be so confusing. Same for [[Phantom Dancer]] and [[Force of Nature]][/quote]

[quote=Yabuki]why don't they say 12% movement speed then? LOL and thanks for the AP explanation, seems a bit redundant to have a % mastery way before a flat rate mastery, or even have the two distinctions at all, but i guess RIOT has their reasons.[/quote]

[quote=Luther3000]Oh, and generally Armour Pen is referred to as 'ArP', because Ability Power is shortened to 'AP'. Just saying cause I was a little confused when you said AP. :P[/quote]

[quote=Temzilla][quote=Luther3000] Oh, and generally Armour Pen is referred to as 'ArP', because Ability Power is shortened to 'AP'. Just saying cause I was a little confused when you said AP. :P [/quote] Attack Power was shortened to AP, so i think even if Armor Pen was the only "AP" it would still get called ArP because of WoW die hards.[/quote]