People often argue League of Legends to be a simple game. Sure, not every champion has an absolutely unique ability that no other champion has. Sure, there's no extremely complex mechanic that only die-hard players can master. Sure, it takes less actions per minute than Starcraft, and requires fewer keys to play than World of Warcraft. I would go into why Riot designed the game the way they did, but that'd be a long debate with many sides and arguments.

Instead, I'd rather go into the little details of this "simple" game we call League of Legends. Even if League of Legends can be argued to be "simple" compared to other games, it has a lot more complexity than many realize. I'm not talking about the strategy, the team work, the tactics, or team compositions. I'm talking about the lesser-known interactions between items and abilities.

A discussion about a thread sparked me to write this, about the interactions between Thornmail and Damage Shields. As a result, I want to list some of the lesser-known interactions and calculations of the game. I know I don't know all of them, so please feel free to add more! Also, please correct me if I am wrong.


Vision/Sight:
- Neutral minions cannot be line-of-sighted by brush or walls. They will just keep chasing you until they reach the end of their leash
- When revealed in the brush for attacking an enemy unit, you are revealed for 5 seconds
- If you have no target and damage an enemy you cannot see, they will become your target and you can see their items/buffs, but not their current health/mana
- Several skills can be used to scout, such as Heimerdinger's Grenades, Anivia's Crystallize, Malzahar's Call of the Void, etc.

Mobility:
- Blink-like abilities (ie. Flash, Arcane Shift, Rift Walk, etc.) will take you to the nearest valid position closest to your targeted location (ie. can pop you on the other side of a wall as long as you cast it more than halfway across)
- Dash-like abilities (ie. Shadow Dash, Unstoppable Force, Distortion, etc.) will only fully move you to your targeted location if your champion can legally stand there. Otherwise, you are moved to the closest legal location on the way

Wards:
- Wards can be used in conjunction with blink-strikes (ie. Shunpo, Leap Strike, Shadow Dance, etc.) to "Flash" to a location. [Shadow Dance requires an enemy ward]
- Wards can be used to block Powerball, Body Slam, and skill shots (ie. Rocket Grab, Dark Binding, Javelin Toss, etc.)
- Wards are placed at the closest wardable position to the targeted location (can be placed over walls by casting at least over half way through the wall)
- Wards only receive physical damage, and only when they are visible

Crowd Control/Debuffs:
- You can interrupt movement-based abilities (ie. Audacious Charge, Distortion, Pounce, etc.) with abilities that move the target (ie. Heroic Charge, Crystallize, Pillar of Filth, etc.)
- Knock-ups are unaffected by Crowd Control Reduction
- Knock-backs are unaffected by Crowd Control Reduction
- Suppression is unaffected by Crowd Control Reduction
- Suppression can be broken out of by cleansing abilities (ie. Remove Scurvy, Unbreakable Will, etc.)
- Even if the suppression effect of Urgot's ultimate is blocked, he will swap with his target after his channeling is complete
- Healing Reduction and Spirit Visage do not affect Life Steal

Abilities/Buffs:
- Mordekaiser does not receive shields for damage absorbed by damage shields
- Shields and Mordekaiser's passive shields are affected by damage mitigation
- Death Lotus is dynamically calculated (affected by increased/decreased AP/AD while in use)
- Noxious Trap's damage is calculated upon detonation
- Abilities that bounce can only bounce to visible targets
- Deadly Venom (Twitch passive) deals true damage
- Takedown's bonus damage works against structures
- Takedown's bonus damage does not crit
- Power Fist's bonus damage works against structures
- Power Fist doubles the damage granted by Sheen/Trinity Force/Lich Bane
- Siphoning Strike's bonus damage works against structures
- Red Lizard Buff deals true damage
- Red Lizard Buff grants melee 30% Movement Speed reduction on hit, while ranged inflicts 15%

- Abilities such as Tides of Blood, Soul Shackles and Death Lotus can "lock on" and target invisible units, firing their projectiles and damage as normal. [Marnelos]

Items:
- Sheen/Trinity Force/Lich Bane's damage cannot normally be criticaled
- Frozen Mallet grants melee 40% Movement Speed reduction on hit, while ranged inflicts 30%
- Life Leech is treated as an "On-Hit" effect, while Spell Vamp works for all abilities that don't proc on-hits (except things like Toxic Shot)
- Frozen Mallet is an "On-Hit" effect, while Rylai's works for all damaging abilities that don't proc on-hits (except things like Toxic Shot)
- Quicksilver Sash can cleanse any enemy debuff, including ones such as Ignite and Suppression
- Items with similar UNIQUE Passive, item-unique non-stat, effects such as Wriggle's Lantern and Madred's Razor do not stack with each other. UNIQUE Passive stats do stack, though, such as Youmuu's Ghostblade and Brutalizer's Armor Penetration, or Frozen Heart and Glacial Shroud's Cooldown Reduction
- Thornmail reflects damage even if a damage shield absorbs all of the damage. It is equal to as if you had no damage shield on

Stats:
- Cooldown Reduction is hard-capped at 40% reduction
- Attack Speed is hard-capped at 2.5 attacks per second
- Attack Speed reduction is multiplicative
- Attack Speed increase is additive
- Dodge is multiplicative
- Boots 1 grants 50 Movement Speed, while each movement point after that is 20 Movement Speed
- Movement Speed is soft-capped
- Additional Movement Speed is additive (ie. 2x Zeal = 1.00 + 2 x .08 = 1.16, rather than 1.08 x 1.08 = 1.1664 )



Calculations:
Physical Damage * ( 1 - [ Net Armor / [ |Net Armor| + 100 ] ] ) = net Physical Damage
Magical Damage * ( 1 - [ Net Magic Resist / [ |Net Magic Resist| + 100 ] ] ) = net Magical Damage
True Damage = True Damage
NOTE: A net armor of 100 doubles your effective health against physical damage (receiving 50% damage means you need 2x the physical damage to die), while -100 net armor reduces your effective health by 33% (receive 50% more physical damage...for example if your health is 900, and they have a base damage of 100, you'd normally take 9 hits to die, but with 1.5x damage you'd take 6 hits to die).

From items:
Percent Reduction > Flat Reduction > Flat Penetration > Percent Penetration

Ex:
Dealing 1000 physical damage
Champion has 100 Armor
Nidalee Bushwhack for 20% is applied
One stack of Black Cleaver (12 Armor Reduction) is applied
20 Armor Penetration
Last Whisper (40% Penetration)

Net Armor = ( 100 Armor * 0.8 - 12 - 20 ) * 0.6 = 48 * 0.6 = 28.8
Net reduction = 28.8 / ( 100 + 28.8 ) = 28 / 128.8 = 0.2174
Net damage = 1000 * ( 1 - 0.2174 ) = 1000 * 0.7826 = 782.6 damage