Should flag

Bounce / elastic easing

CSS bounce animation

animation: bounce 1s infinite

Elastic cubic-bezier

cubic-bezier(0.68, -0.55, 0.265, 1.55)

Layout property transitions

transition: width

Animating width causes layout thrash.

transition: height

Animating height causes layout thrash.

transition: padding

Animating padding causes layout thrash.

transition: margin

Animating margin causes layout thrash.

transition: max-height

Use grid-template-rows instead.

transition: width, height

Multiple layout properties.

transition: width, opacity

Layout property mixed with OK property.

transition-property: width

Longhand form.

Should pass

Good easing

Smooth fade in

animation: fadeIn with exponential ease-out

Ease-out quart

cubic-bezier(0.25, 1, 0.5, 1) — smooth deceleration

Ease-out expo

cubic-bezier(0.16, 1, 0.3, 1) — natural feel

Safe transitions (transform / opacity / color only)

transition: transform

Transform is GPU-accelerated and safe.

transition: opacity

Opacity is GPU-accelerated and safe.

transition: color, background-color

Color transitions are paint-only, no layout.

transition: box-shadow

Shadow transitions are paint-only.

transition: all

Too common to flag — usually paired with transform/opacity.

transition: transform, opacity, box-shadow

Multiple safe properties combined.