Neumorphism (soft UI)
One flat background color, with controls that look extruded from it or pressed into it via paired light and dark soft shadows.
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What it is
Neumorphism (soft UI) keeps every element the exact same color as the background, then makes it look extruded from that surface with a pair of shadows: a dark one on the bottom-right and a light one on the top-left, both soft. Flip both to inset and the element looks pressed in instead. It went viral around 2019 off a Dribbble concept shot and got the name 'neumorphism' as a mashup of new plus skeuomorphism.
It's at its best in small doses on things that really are physical metaphors: media transport controls, thermostat and smart-home dials, toggles, calculator keypads. The pressed-in state is genuinely satisfying because the shadow inversion matches what your hand expects.
Gotcha: it's an accessibility problem by construction. All the contrast lives in the shadows, so the element and its background have a contrast ratio of 1:1 and the boundary vanishes for anyone with low vision or a dim screen. Nothing looks clickable, disabled looks identical to enabled, and the whole effect breaks the moment the background is a photo, a gradient, or a different theme. If you use it, pair it with a real border or a color accent on interactive elements.
Ask AI for it
Style these components as neumorphism (soft UI). Set the page and every card, button, and input to the same background color (#E0E5EC). Give raised elements box-shadow: 9px 9px 18px #A3B1C6, -9px -9px 18px #FFFFFF, with a 16px to 20px corner radius and no border. Give pressed or active states the same shadows with 'inset' and slightly smaller blur. Use a muted mid-grey text color and thin geometric icons. Keep the light source consistently top-left across the whole screen, and add a visible accent color or outline to anything clickable so the affordance survives the low contrast.