Responsive design

@mixin for-phone-only {
  @media (max-width: 599px) { @content; }
}
@mixin for-tablet-portrait-up {
  @media (min-width: 600px) { @content; }
}
@mixin for-tablet-landscape-up {
  @media (min-width: 900px) { @content; }
}
@mixin for-desktop-up {
  @media (min-width: 1200px) { @content; }
}
@mixin for-big-desktop-up {
  @media (min-width: 1800px) { @content; }
}

// usage
.my-box {
  padding: 10px;
  
  @include for-desktop-up {
    padding: 20px;
  }
}

header {
    color: red;
       
        @media only screen and (min-width : 768px) { color: green; }
               
        @media only screen and (min-width : 1024px) { color: blue; }
               
}

section {
    color: green;
       
        @media only screen and (min-width : 768px) { color: blue; }
               
        @media only screen and (min-width : 1024px) { color: red; }
               
}

header {
  color: red;
}
@media only screen and (min-width: 768px) {
  header {
    color: green;
  }
}
@media only screen and (min-width: 1024px) {
  header {
    color: blue;
  }
}

section {
  color: green;
}
@media only screen and (min-width: 768px) {
  section {
    color: blue;
  }
}
@media only screen and (min-width: 1024px) {
  section {
    color: red;
  }
}