CSS component boundaries and transitions: twelve decisions

Check which styling surfaces are public and which behavior an application must supply.

Review the decisions

• CSS :host: make a component variant an explicit host contract
• CSS ::slotted(): style only the assigned element
• CSS view-transition-name: give one live element one transition identity
• CSS @supports selector(): gate a relational selector safely

Other checks

• CSS Quizzes
• CSS rendering contracts quiz

Common Mistakes

• Do not confuse paint with semantics.
• Do not expect CSS to start or manage an application transition.