New game mode: Opportunity

Welcome to Opportunity Mode, a temporary featured game mode that will test both your restraint, and your eye for seizing the moment when it's time to strike.

Core Feature:

When a champion's skills (and if it's not too much work, items and summoner spellls) would go on cooldown after use, concurrently, that skill gets shaded with a blue tint for 3 seconds: a window of opportunity. The champion may use this skill again at no mana cost, but if they do, there is an opportunity cost - the cooldown of the skill starts ticking again starting at double the value of what it would have been.

Example: Lvl 1 Annie goes bot lane with Incinerate (W, 8 sec c/d). She casts it, and simultaneously her 8 second spell c/d starts, as well as her 3 second Opportunity c/d. She could cast it again after one second had passed, for no mana, but resetting the Incinerate cooldown to 16 seconds. She could cast it again after 3 seconds, and Incinerate's c/d would still reset to 16. If she waits 4 seconds, it's too late to get the bonus mana-free cast, but it will be available to her in just 4 more seconds.

But this is a featured game mode, and you want to really get wild. So, as this refreshed double cooldown would begin, the skill is now tinted red for 3 seconds: the skill may be used again a 3rd time at double the original mana cost, but if they do, the skill goes on cooldown once more, this time with a cooldown duration 4x that of its original value.

Example: level 9 Syndra with Force of Will (W) maxed is running away from level 9 Garen. Garen has boots and is faster, so Syndra uses FoW (8 sec c/d) to slow the approaching Garen. Garen uses Judgement (8 sec c/d) to break the slow effects and really close hard on Syndra. She's still about 4 seconds worth of running away from her tower, so now she has a choice to make. She could continue momentarily slowing Garen (up to 2 more times), but since he used his Judgement after her Force of Will, it's likely that he will rinse-and-repeat his cc break. She could get spun on and die, but dying is for the weak, and surrendering for the French, so she chooses to 3x Dark Sphere (q) followed by 3x Unleashed Power (ult, 100 sec c/d).

Boom. Dead Garen. Unfortunately for Syndra, but quite fortunate for her lane opponent Anivia, Syndra's ult is now on a 400 second cooldown. While Syndra took her opportunity to save her own life, and pick up a kill in the process, surely the enemy team will use their new window of opportunity to strike back while this important spell is on an extended cooldown.

Secondary Features:

Global, passive tenacity buff.

Exceptions:

Spells with a cooldown (or through cdr gain a cooldown) less than 4 seconds.

Certain skills on a case by case basis, especially channeled skills (Karthus ult comes to mind).