Why top and left part of input element appear darker than other sides?

I am applying this simple css on an input element for it to have a uniform, thin border which is lightgray in color, on ALL sides. However, I find that two of the sides appear darker ? or it is a shadow property of some kind ? What can be done to make it uniform on all sides ?

input {
  border-width: thin;
  border-color: lightgray;
  box-shadow: none;
  outline: none;
}

<input>

>Solution :

The default value for border-style on input elements is usually inset. You need to set it to solid.

Actually it usually makes sense to use the border shorthand and always set width, color and style at the same time:

border: lightgray thin solid;