Flash

The element's opacity flickers irregularly like a failing light.

Add a "Flicker" effect (also called flickering) to [where].
The element should stay steady most of the time and dim in short, uneven stutters like a failing neon light.
Keep the timing irregular rather than evenly spaced, avoid rapid full-strength flashing, and stop it for users who prefer reduced motion.

The element blinks on with rapid opacity flashes like a faulty neon sign before staying visible.

Add a "Flicker In" entrance animation to [where].
The element should blink on and off a few times at irregular intervals, like a faulty neon sign, before staying lit: sharp flashes with no movement.
Play it once, keep the flashes few and slow enough to be safe for people sensitive to flashing light, and show it steadily lit when the user prefers reduced motion (prefers-reduced-motion).

The element gently scales or fades in and out repeatedly.

Add a "Pulse" effect (also called pulsing) to [where].
The element should gently swell and ease back in a slow, steady rhythm: subtle, with no bounce.
Loop it seamlessly without shifting the surrounding layout, and stop it for users who prefer reduced motion.

Text glows like a neon tube and flickers or pulses.

Add a "Neon Glow Text" effect (also called a neon sign flicker or glowing text) to [where].
The text should glow like a neon tube with a soft, steady light, and now and then flicker off briefly like a real sign.
Keep the flicker occasional rather than rapid, since fast flashing can harm some users, and keep the glow steady for users who prefer reduced motion.

The element wobbles side to side with slight rotation like a head shaking no.

Add a "Head Shake" attention effect (also called headshake or no shake) to [where].
The element should turn quickly side to side with a slight twist, like a head shaking no, each turn smaller than the last before it settles.
Play it once each time it is triggered, such as on a rejected action, and keep the surrounding layout from moving.

The element scales in a double-beat rhythm like a beating heart.

Add a "Heartbeat" effect (also called heart beat) to [where].
The element should swell and relax in a quick double beat, then rest briefly before the next beat, like a beating heart.
Loop it seamlessly with the rest kept between beats, and stop it for users who prefer reduced motion.