<!-- using "div" instead of "a" because for unkown reasons it's not working with "a" (probably bug)-->
<nav>
  <div class="nav-item" href="#"><i>🏠</i>home</div>
  <div class="nav-item" href="#"><i>🔍</i>search</div>
  <div class="nav-item" href="#"><i>🖤</i>likes</div>
  <div class="nav-item" href="#"><i>🔔</i>notification</div>
  <div class="nav-item" href="#"><i>👱</i>profile</div>
</nav>

<script>
if (CSS.paintWorklet) {              CSS.paintWorklet.addModule('/t_afif/pen/eYRqKXQ.js');
} else {
  alert("Your browser cannot run this demo. Consider Chrome or Edge instead")
}
</script>
@property --radius{
  syntax: '<length>';
  inherits: true;
  initial-value: 0;
}
@property --d{
  syntax: '<length>';
  inherits: true;
  initial-value: 18px;
}

body, nav, div { display: grid }

body {
	place-content: center;
	margin: 0;
	height: 100vh;
	background: 
		repeating-radial-gradient(circle at 25% 25%, 
				transparent 0, hsla(0, 0%, 0%, .2) 1px 4px, transparent 5px 8px)
		#f03
}
nav {
	grid-auto-flow: column;
	padding: 0 20px;
	border-radius: 10px;
	background:
    linear-gradient(#fff 0 0) left,
    linear-gradient(#fff 0 0) right;
  background-size:20px 100%;
  background-repeat:no-repeat;
	font: .625em/ 1.5 ubuntu, sans-serif;
}

.nav-item {
	box-sizing: border-box;
  cursor:pointer;
	place-content: center;
	width: 7.5em; 
  height: 7.5em;
	color: #000;
	text-align: center;
	text-decoration: none;
	text-transform: capitalize;
  position:relative;
  z-index:0;
}
.nav-item i {
  font-style:initial;
	font-size: 2em;
  transition: .4s;
	filter: brightness(0) contrast(var(--hl,0))
}
.nav-item::after {
  content:"";
  position:absolute;
  z-index:-1;
 inset: -18px 0 0 0;
 background: #fff;
 --t: 0;
 --path: 0 18px,10px 18px 50px,50% var(--d,18px) 50px,calc(100% - 10px) 18px 50px,100% 18px,100% 100%,0 100%;
  --radius: 0px;
  -webkit-mask:paint(rounded-shape);
  transition:--d .4s;
}

.nav-item:hover::after {
  --d:0;
}
.nav-item:hover i {
  transform:translateY(-15px);
}


.nav-item:focus { outline: none }
.nav-item:focus,.nav-item:hover { --hl: 1 }
registerPaint('rounded-shape', class  {

  static get inputProperties() {
    return [
      '--path',
      '--radius',
      '--border',
      '--t',
      '--dash'
    ]
  }
  
  paint(ctx, size, properties) {
    const points = properties.get('--path').toString().split(',');
    var Ppoints = [];
    var Cpoints = [];
    var Radius = [];
    const r = parseFloat(properties.get('--radius').value);
    const b = parseFloat(properties.get('--border').value);
    const d = properties.get('--dash').toString().split(',');
    const t = parseInt(properties.get('--t'));
    const w = size.width;
    const h = size.height;
    
    const cc = function(x,y) {
      var fx=0,fy=0;
      if (x.indexOf('calc') > -1) {
        var tmp = x.replace('calc(','').replace(')','');
        if (tmp.indexOf('+') > -1) {
          tmp = tmp.split('+');
          fx = (parseFloat(tmp[0])/100)*w + parseFloat(tmp[1]);
        } else {
          tmp = tmp.split('-');
          fx = (parseFloat(tmp[0])/100)*w - parseFloat(tmp[1]);
        }
      } else if (x.indexOf('%') > -1) {
        fx = (parseFloat(x)/100)*w;
      } else if(x.indexOf('px') > -1) {
        fx = parseFloat(x);
      }
      
      if (y.indexOf('calc') > -1) {
        var tmp = y.replace('calc(','').replace(')','');
        if (tmp.indexOf('+') > -1) {
          tmp = tmp.split('+');
          fy = (parseFloat(tmp[0])/100)*h + parseFloat(tmp[1]);
        } else {
          tmp = tmp.split('-');
          fy = (parseFloat(tmp[0])/100)*h - parseFloat(tmp[1]);
        }
      } else if (y.indexOf('%') > -1) {
        fy = (parseFloat(y)/100)*h;
      } else if(y.indexOf('px') > -1) {
        fy = parseFloat(y);
      }
      return [fx,fy];
    }
   
    var N = points.length;
    for (var i = 0; i < N; i++) {
      var j = i-1;
      if(j<0) j=N-1;
      
      var p = points[i].trim().split(/(?!\(.*)\s(?![^(]*?\))/g);
      if(p[2])
        Radius.push(parseInt(p[2]));
      else
        Radius.push(r);
      p = cc(p[0],p[1]);
      Ppoints.push([p[0],p[1]]);
      var pj = points[j].trim().split(/(?!\(.*)\s(?![^(]*?\))/g);
      pj = cc(pj[0],pj[1]);
      Cpoints.push([p[0]-((p[0]-pj[0])/2),p[1]-((p[1]-pj[1])/2)]);
    }
    ctx.beginPath();
    ctx.moveTo(Cpoints[0][0],Cpoints[0][1]);
    var i;
    var rr;
    for (i = 0; i < (Cpoints.length - 1); i++) {
      var angle = Math.atan2(Cpoints[i+1][1] - Ppoints[i][1], 
                             Cpoints[i+1][0] - Ppoints[i][0]) -
                  Math.atan2(Cpoints[i][1] - Ppoints[i][1], 
                             Cpoints[i][0] - Ppoints[i][0]);
      if (angle < 0) {
        angle += (2*Math.PI)
      }
      if (angle > Math.PI) {
        angle = 2*Math.PI - angle
      }
      var distance = Math.min(Math.sqrt((Cpoints[i+1][1] - Ppoints[i][1]) ** 2 + 
                                        (Cpoints[i+1][0] - Ppoints[i][0]) ** 2),
                              Math.sqrt((Cpoints[i][1] - Ppoints[i][1]) ** 2 + 
                                        (Cpoints[i][0] - Ppoints[i][0]) ** 2));
      rr = Math.min(distance * Math.tan(angle/2),Radius[i]);
      ctx.arcTo(Ppoints[i][0], Ppoints[i][1], Cpoints[i+1][0],Cpoints[i+1][1], rr);
    }
  var angle = Math.atan2(Cpoints[0][1] - Ppoints[i][1], 
                             Cpoints[0][0] - Ppoints[i][0]) -
                  Math.atan2(Cpoints[i][1] - Ppoints[i][1], 
                             Cpoints[i][0] - Ppoints[i][0]);
   if (angle < 0) {
      angle += (2*Math.PI)
   }
   if (angle > Math.PI) {
      angle = 2*Math.PI - angle
   }
   var distance = Math.min(Math.sqrt((Cpoints[0][1] - Ppoints[i][1]) ** 2 + 
                                        (Cpoints[0][0] - Ppoints[i][0]) ** 2),
                              Math.sqrt((Cpoints[i][1] - Ppoints[i][1]) ** 2 + 
                                        (Cpoints[i][0] - Ppoints[i][0]) ** 2));
    rr = Math.min(distance * Math.tan(angle/2),Radius[i]);
    ctx.arcTo(Ppoints[i][0], Ppoints[i][1], Cpoints[0][0],Cpoints[0][1], rr);
    ctx.closePath();
    
    
    if(t==0) {
      ctx.fillStyle = '#000';
      ctx.fill();
    } else {
      ctx.setLineDash(d);
      ctx.lineWidth = 2*b;
      ctx.strokeStyle = '#000';
      ctx.stroke();
    }
  }

})
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