
Spell Activation Overlay
This WoW Classic addon mimics Spell Activation Overlays, formerly known as Spell Alerts, which were introduced in Cataclysm.
For example, Frost Death Knights can have procs for Rime and Killing Machine, while Enhancement Shamans have stacks of Maelstrom Weapon.
This addon also makes relevant buttons glow. For example, a Fire mage triggering Hot Streak will have a glowing Pyroblast button.
There is nothing to configure. Just install the addon and enjoy your procs!
Death Knight: Killing Machine, Rime, Rune Strike (glowing button only)

Killing Machine and Rime
Druid: Eclipse (Lunar), Eclipse (Solar), Nature's Grace (optional), Predatory Strikes, Omen of Clarity, Omen of Clarity (Feral), Elune's Wrath (4p Tier 8 set), Wrath of Elune (4p PvP set Season 5/6/7/8)

Eclipse (Lunar) and Omen of Clarity

Eclipse (Solar) and Omen of Clarity

Nature's Grace (Blue-ish)

Nature's Grace (Green-ish)

Predatory Strikes

Omen of Clarity

Omen of Clarity (Feral)
Hunter: Improved Steady Shot, Lock and Load, Counterattack (glowing button only), Kill Shot (glowing button only)

Improved Steady Shot

Lock and Load
Mage: Missile Barrage, Clearcasting (optional), Impact, Firestarter, Hot Streak, Heating Up, Hot Streak + Heating Up (optional), Brain Freeze, Fingers of Frost

Missile Barrage

Clearcasting (weak effect)

Clearcasting (strong effect)

Clearcasting (strong effect alongside Hot Streak)

Impact

Firestarter

Heating Up, then Hot Streak

Heating Up and Hot Streak at the same time

Brain Freeze

Fingers of Frost
Paladin: Infusion of Light, Art of War, Hammer of Wrath (glowing button only)

Infusion of Light

Art of War
Priest: Surge of Light, Serendipity

Surge of Light and Serendipity
Rogue: Riposte

Riposte
Shaman: Elemental Focus, Maelstrom Weapon, Tidal Waves (optional)

Elemental Focus

Maelstrom Weapon

Tidal Waves
Warlock: Nightfall, Molten Core, Decimation, Backlash, Empowered Imp, Drain Soul (glowing button only, optional)

Nightfall

Molten Core

Decimation

Backlash

Empowered Imp
Warrior: Sudden Death, Bloodsurge, Sword and Board, Overpower (glowing button only), Revenge (glowing button only), Execute (glowing button only), Victory Rush (glowing button only)

Sudden Death

Bloodsurge

Sword and Board
Contribution
If you wish to contribute, please come by and visit the Discord server.
You can also file an Issue or send a Pull Request to the github repository.