Generated by SassMeister.com.

SassMeister-input-HTML.html

<p>
  <a href="#0">Button</a>
</p>

<p>
  <button>Button</button>
</p>

<p>
  <input type="submit" value="Button" />
</p>

<hr />

<p>
  <a href="#0" class="c-btn">Button</a>
</p>

<p>
  <button class="c-btn">Button</button>
</p>

<p>
  <input type="submit" value="Button" class="c-btn" />
</p>

<hr />

<p>
  <a href="#0" class="c-btn  c-btn--primary">Button</a>
</p>

<p>
  <button class="c-btn  c-btn--primary">Button</button>
</p>

<p>
  <input type="submit" value="Button" class="c-btn  c-btn--primary" />
</p>

SassMeister-input.scss

// ----
// Sass (v3.4.20)
// Compass (v1.0.3)
// ----

$color: #1b78cc;

html {
  font: menu;
  font-size: 12px;
  line-height: 1.5;
}

a {
  color: $color;
  text-decoration: none;

  &:hover,
  &:focus {
    text-decoration: underline;
  }

}

.c-btn {
  font: inherit;
  border: none;
  background: none;
  cursor: pointer;
  display: inline-block;
  padding: 9px 18px;
  text-decoration: underline;
  font-weight: bold;
  color: $color;
  letter-spacing: 0.05em;
}

.c-btn--primary {
  font-weight: normal;
  text-transform: uppercase;
  text-decoration: none;
  background-color: $color;
  color: white;

  &:hover,
  &:focus {
    text-decoration: none;
  }

}

SassMeister-output.css

html {
  font: menu;
  font-size: 12px;
  line-height: 1.5;
}

a {
  color: #1b78cc;
  text-decoration: none;
}
a:hover, a:focus {
  text-decoration: underline;
}

.c-btn {
  font: inherit;
  border: none;
  background: none;
  cursor: pointer;
  display: inline-block;
  padding: 9px 18px;
  text-decoration: underline;
  font-weight: bold;
  color: #1b78cc;
  letter-spacing: 0.05em;
}

.c-btn--primary {
  font-weight: normal;
  text-transform: uppercase;
  text-decoration: none;
  background-color: #1b78cc;
  color: white;
}
.c-btn--primary:hover, .c-btn--primary:focus {
  text-decoration: none;
}

SassMeister-rendered.html

<p>
  <a href="#0">Button</a>
</p>

<p>
  <button>Button</button>
</p>

<p>
  <input type="submit" value="Button" />
</p>

<hr />

<p>
  <a href="#0" class="c-btn">Button</a>
</p>

<p>
  <button class="c-btn">Button</button>
</p>

<p>
  <input type="submit" value="Button" class="c-btn" />
</p>

<hr />

<p>
  <a href="#0" class="c-btn  c-btn--primary">Button</a>
</p>

<p>
  <button class="c-btn  c-btn--primary">Button</button>
</p>

<p>
  <input type="submit" value="Button" class="c-btn  c-btn--primary" />
</p>