run button

index.html

<button type="button" id="runbutton">
  <svg width="18" height="18" viewBox="0 0 24 24" style="vertical-align: text-bottom;">
    <path d="M8 5v14l11-7z"></path>
  </svg>
  Run
</button>

<button type="button" class="error" id="runbutton">
  <svg width="18" height="18" viewBox="0 0 24 24" style="vertical-align: text-bottom;">
    <path d="M8 5v14l11-7z"></path>
  </svg>
  Run
</button>

<button type="button" class="error2" id="runbutton">
  <svg width="17" height="17" style="position:relative; top: 3px; margin:-3px 2px 0 0;" viewBox="0 0 24 24">
    <path d="M5,3H19A2,2 0 0,1 21,5V19A2,2 0 0,1 19,21H5A2,2 0 0,1 3,19V5A2,2 0 0,1 5,3M13,13V7H11V13H13M13,17V15H11V17H13Z"></path>
  </svg>
  Run
</button>

main.dart

//see html and css
void main() {}

style.css

button {
  outline: none;
  color: #222;
  fill: #222;
  border: 1px solid #222;
  border-radius: 2px;
  font-family: 'Roboto', sans-serif;
  font-size: 12pt;
  line-height: 18px;
  height: 24px;
  cursor: pointer;
  padding: 2px 7px;
  padding-right: 11px;
  transition: 100ms;
  min-width: 75px;
  background-image: linear-gradient(to bottom, #2d7231, #214321);
}

button.error {
  background-image: linear-gradient(to bottom, #ac6356, #673a33);
  color: #222;
  fill: #222;
}
button.error2 {
  background-image: linear-gradient(to bottom, #ac6356, #673a33);
  color: #222;
  fill: #222;
  padding: 2px 13px 2px 14px;  
}

button:hover {
  color: rgba(255, 255, 255, 0.7
  );
  fill: rgba(255, 255, 255, 0.7
  );
}

button:active {
  background: rgba(255, 255, 255, 0.2);
}

button[disabled] {
  color: #555;
  fill: #555;
  pointer-events: none;
  border-color: #272727;
  background-color: #3b3b3b;
  background-image: none;
}