JSFiddle - React, Tailwind, and code Playground

HTML

<div id="botones">
        <ul id="menu-bar">
            <li id="botones_principales"><a href="#">Principal</a></li>
               <li id="botones_principales"><a href="#">Acerca de m&iacute;</a></li>
               <li id="botones_principales"><a href="#">Curr&iacute;culum Vitae</a></li>
               <li id="botones_principales"><a href="#">Proyectos personales</a></li>
               <li id="botones_principales"><a href="#">Contacto</a></li>
           </ul>
       </div>

CSS

#botones {
text-align:center;
}

#botones_principales {
display:inline;
list-style-type:none;
padding:5px;

}

#menu-bar {
 width: auto;
 margin: 0px 0px 0px 0px;
 padding: 5px 8px 0px 5px;
 height: auto;
 line-height: 100%;
 border-radius: 9px;
 -webkit-border-radius: 9px;
 -moz-border-radius: 9px;
 box-shadow: 3px 5px 7px #666666;
 -webkit-box-shadow: 3px 5px 7px #666666;
 -moz-box-shadow: 3px 5px 7px #666666;
 background: #8B8B8B;
 background: linear-gradient(top,  #828282,  #C9C9C9);
 background: -ms-linear-gradient(top,  #828282,  #C9C9C9);
 background: -webkit-gradient(linear, left top, left bottom, from(#828282), to(#C9C9C9));
 background: -moz-linear-gradient(top,  #828282,  #C9C9C9);
 border: solid 1px #6D6D6D;
 position:relative;
 z-index:999;
}
#menu-bar li {
 margin: 0px 0px 6px 0px;
 padding: 0px 6px 0px 6px;
 display: inline-block;
 position: relative;
 list-style: none;
}
#menu-bar a {
 font-weight: bold;
 font-family: arial;
 font-style: normal;
 font-size: 12px;
 color: #E7E5E5;
 text-decoration: none;
 display: block;
 padding: 6px 20px 6px 20px;
 margin: 0;
 margin-bottom: 6px;
 border-radius: 10px;
 -webkit-border-radius: 10px;
 -moz-border-radius: 10px;
 text-shadow: 2px 2px 3px #000000;
}
#menu-bar li ul li a {
 margin: 0;
}
#menu-bar .active a, #menu-bar li:hover > a {
 background: #0399D4;
 background: linear-gradient(top,  #EBEBEB,  #A1A1A1);
 background: -ms-linear-gradient(top,  #EBEBEB,  #A1A1A1);
 background: -webkit-gradient(linear, left top, left bottom, from(#EBEBEB), to(#A1A1A1));
 background: -moz-linear-gradient(top,  #EBEBEB,  #A1A1A1);
 color: #444444;
 -webkit-box-shadow: 0 1px 1px rgba(0, 0, 0, .2);
 -moz-box-shadow: 0 1px 1px rgba(0, 0, 0, .2);
 box-shadow: 0 1px 1px rgba(0, 0, 0, .2);
 text-shadow: 2px 2px 3px #FFFFFF;
}
#menu-bar ul li:hover a, #menu-bar li:hover li a {
 background: none;
 border: none;
 color: #666;
 -box-shadow: none;
 -webkit-box-shadow: none;
 -moz-box-shadow: none;
}
#menu-bar ul a:hover {
...