Flicker

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 blinks by quickly toggling its opacity.

Add a "Flash" attention effect (also called blink) to [where].
The element should blink by quickly fading out and back in twice, then stay fully visible.
Play it once rather than as an endless blink, and skip it for users who prefer reduced motion, since fast blinking can be uncomfortable.

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.

Text jitters with sliced offsets and red/cyan colour splits like a broken signal.

Add a "Glitch Text" hover effect (also called text glitch or RGB split glitch) to [where].
While the pointer is over the text, it should jitter in quick, snappy bursts: thin horizontal slices jump sideways and two colored copies split apart like a broken signal, then settle back when the pointer leaves.
Keep the real text in the document only once so screen readers don't read the copies, and show the same effect on keyboard focus.

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.

The element skews back and forth with decaying amplitude like a wobbling jelly.

Add a "Jello" attention effect (also called jelly) to [where].
The element should skew back and forth like a wobbling jelly, strong at first and quickly settling to rest.
Play it once when triggered, and keep the element's footprint so nearby content does not shift.