body { background: blueviolet }
body::after{ content: "I don't know what you are using to click" }

@media (pointer: coarse) {
  body { background: crimson }
  body::after{ content: "Your primary input mechanism is a finger" }  
}

@media (pointer: fine) {
  body { background: goldenrod }
  body::after{ content: "Your primary input mechanism is a mouse" }
}