<div class="hexagone" style="--path:25% 0%, 75% 0%, 100% 50%, 75% 100%, 25% 100%, 0% 50%"></div>
<div class="triangle" style="--path:50% 0%, 0% 100%, 100% 100%;background:url(https://picsum.photos/id/1061/300/300) center/cover;"></div>
<div class="star" style="--path:50% 0%, 61% 35%, 98% 35%, 68% 57%, 79% 91%, 50% 70%, 21% 91%, 32% 57%, 2% 35%, 39% 35%;background:gold"></div>
<div class="arrow" style="--path:40% 0%, 40% 35%, 100% 35%, 100% 65%, 40% 65%, 40% 100%, 0% 50%;background:green"></div>
<div class="custom" style="--path:50% 0%, 50% 50%, 100% 60%, 75% 100%, 25% 100%, 0% 60%, 10% 20%;background: conic-gradient(at 53% 47%, orange,pink,purple);"></div>

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

div[class] {
  display:inline-block;
  width:150px;
  cursor:pointer;
  background:red;
  margin:20px;
  --radius:5px;
  transition:--radius 1s;
  clip-path:polygon(var(--path));
  -webkit-mask:paint(rounded-shape);
}
div[class]:hover {
  --radius:80px;
}
div[class]::before {
   content:"";
   display:block;
}

.hexagone::before,
.triangle::before{
   padding-top:86.6%;
}
.star::before,
.custom::before{
   padding-top:100%;
}
.arrow::before {
   padding-top:70%;
}
registerPaint('rounded-shape', class  {

  static get inputProperties() {
    return [
      '--path',
      '--radius',
      '--border',
      '--dash'
    ]
  }
  
  paint(ctx, size, properties) {

    const points = properties.get('--path').toString().split(',');
    var Ppoints = [];
    var Cpoints = [];
    const r = parseFloat(properties.get('--radius').value);
    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);
      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;
    for (i = 0; i < (Cpoints.length - 1); i++) {
      ctx.arcTo(Ppoints[i][0], Ppoints[i][1], Cpoints[i+1][0],Cpoints[i+1][1], r);
    }
    ctx.arcTo(Ppoints[i][0], Ppoints[i][1], Cpoints[0][0],Cpoints[0][1], r);
    ctx.closePath();
    ctx.fillStyle = '#000';
    ctx.fill();
  }

})
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External JavaScript

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