Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

+ add another resource

JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

Behavior

Auto Save

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                <form>
  <div class="board-wrapper">
    <div class="board-outer">
      <div class="board">
        <div class="board-inner">
          <input type="radio" name="pos11" id="pos11-blue" class="blue" required>
          <input type="radio" name="pos11" id="pos11-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos12" id="pos12-blue" class="blue" required>
          <input type="radio" name="pos12" id="pos12-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos13" id="pos13-blue" class="blue" required>
          <input type="radio" name="pos13" id="pos13-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos21" id="pos21-blue" class="blue" required>
          <input type="radio" name="pos21" id="pos21-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos22" id="pos22-blue" class="blue" required>
          <input type="radio" name="pos22" id="pos22-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos23" id="pos23-blue" class="blue" required>
          <input type="radio" name="pos23" id="pos23-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos31" id="pos31-blue" class="blue" required>
          <input type="radio" name="pos31" id="pos31-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos32" id="pos32-blue" class="blue" required>
          <input type="radio" name="pos32" id="pos32-red" class="red" required>
          <div class="marque"></div>

          <input type="radio" name="pos33" id="pos33-blue" class="blue" required>
          <input type="radio" name="pos33" id="pos33-red" class="red" required>
          <div class="marque"></div>

          <div id="win-blue" class="win-message"><div class="wrapper">Blue wins!</div></div>
          <div id="win-red" class="win-message"><div class="wrapper">Red wins!</div></div>
          <div id="no-winner" class="win-message"><div class="wrapper">It's a draw!</div></div>
        </div>
      </div>
    </div>
  </div>
  <div class="actions">
    <button type="reset">Restart</button>
  </div>
</form>
              
            
!

CSS

              
                * {
	margin:0;
	padding:0;
	box-sizing:border-box;
}
html, body {
	background:#000;
}

/*vars*/
$red:#c50878;
$redhover:rgba(197, 9, 120, .3);
$blue:#5039ff;
$bluehover:rgba(80, 57, 255, .3);

:root {
	--blocksize:20vw;
	--boardsize:60vw;
	--spacing:45vw;
	--winmsgsize:8vw;
}
@media (min-width: 750px) {
	:root {
		--blocksize:150px;
		--boardsize:450px;
		--spacing:400px;
		--winmsgsize:3rem;
	}
}

/*board*/
.board-wrapper {
	overflow:hidden;
	margin:3rem 0 0 calc( 50vw - var(--boardsize) / 2 );
	width:var(--boardsize);
}
.board-outer {
	width:100vw;
}
.board-inner {
	width:var(--boardsize); height:var(--boardsize);
}
.board {
	float:left;
	position:relative;

	&:before {
		position:absolute;
		left:-999px;
		content:counter(player);
	}
	&:after {
		content:counter(player, lower-roman);
		display:inline-block;
		height:0;
		background:grey;
		font-family:monospace;
		letter-spacing:var(--spacing);
		overflow:hidden;
	}
}

/*input radio*/
.board input {
	position:absolute;
	width:var(--blocksize);
	height:var(--blocksize);
	cursor:pointer;
	opacity:0;
	-webkit-appearance:none;

	&:indeterminate {
		display:block;
	}
	&:checked,
	&:checked + input {
		display:none;
	}

	&.blue {
		background:$blue;
	}
	&.red {
		background:$red;
		left:auto !important;
	}

	&[name="pos11"] {
		top:0; left:0;
		& + input { right:calc( 2 * var(--blocksize) ); }
	}
	&[name="pos12"] {
		top:0; left:var(--blocksize);
		& + input { right:var(--blocksize); }
	}
	&[name="pos13"] {
		top:0; left:calc( 2 * var(--blocksize) );
		& + input { right:0; }
	}
	&[name="pos21"] {
		top:var(--blocksize); left:0;
		& + input { right:calc( 2 * var(--blocksize) ); }
	}
	&[name="pos22"] {
		top:var(--blocksize); left:var(--blocksize);
		& + input { right:var(--blocksize); }
	}
	&[name="pos23"] {
		top:var(--blocksize); left:calc( 2 * var(--blocksize) );
		& + input { right:0; }
	}
	&[name="pos31"] {
		top:calc( 2 * var(--blocksize) ); left:0;
		& + input { right:calc( 2 * var(--blocksize) ); }
	}
	&[name="pos32"] {
		top:calc( 2 * var(--blocksize) ); left:var(--blocksize);
		& + input { right:var(--blocksize); }
	}
	&[name="pos33"] {
		top:calc( 2 * var(--blocksize) ); left:calc( 2 * var(--blocksize) );
		& + input { right:0; }
	}
}

/*marque*/
.marque {
	float:left;
	display:flex;
	padding:1px;
	width:var(--blocksize); height:var(--blocksize);
	justify-content:center;
	align-items:center;
	background:#1d1d1d;
	background-clip:content-box;
	&:before {
		content:"";
		position:static;
		display:block;
		width:50%; height:50%;
	}
}

/* marque hover*/
.blue:hover + .red + .marque:before {
	background:$bluehover;
	border-radius:3px;
}
.blue + .red:hover + .marque:before {
	background:$redhover;
	border-radius:50%;
}

/* marque checked*/
.blue:checked + .red + .marque {
	counter-increment:player 2;
	position:relative;
	z-index:100;
	&:before {
		background:$blue;
		border-radius:3px;
	}
}
.blue + .red:checked + .marque {
	counter-increment:player -2;
	position:relative;
	z-index:100;
	&:before {
		background:$red;
		border-radius:50%
	}
}

/* results */
@mixin winners($val) {
	//1st line
	#pos11-#{$val}:checked ~ #pos12-#{$val}:checked ~ #pos13-#{$val}:checked ~ #win-#{$val},
	//2nd line
	#pos21-#{$val}:checked ~ #pos22-#{$val}:checked ~ #pos23-#{$val}:checked ~ #win-#{$val},
	//3rd line
	#pos31-#{$val}:checked ~ #pos32-#{$val}:checked ~ #pos33-#{$val}:checked ~ #win-#{$val},
	//1st column
	#pos11-#{$val}:checked ~ #pos21-#{$val}:checked ~ #pos31-#{$val}:checked ~ #win-#{$val},
	//2nd column
	#pos12-#{$val}:checked ~ #pos22-#{$val}:checked ~ #pos32-#{$val}:checked ~ #win-#{$val},
	//3rd column
	#pos13-#{$val}:checked ~ #pos23-#{$val}:checked ~ #pos33-#{$val}:checked ~ #win-#{$val},
	//1st diagonal
	#pos11-#{$val}:checked ~ #pos22-#{$val}:checked ~ #pos33-#{$val}:checked ~ #win-#{$val},
	//2nd diagonal
	#pos13-#{$val}:checked ~ #pos22-#{$val}:checked ~ #pos31-#{$val}:checked ~ #win-#{$val} {
		display:block;
		& ~ #no-winner {
			display:none;
		}
	}
}

.win-message {
	position:absolute;
	top:0;
	display:none;
    height:100%; width:100%;
	color:#FFF;
	font-size:var(--winmsgsize);
	font-weight:bold;
    z-index:200;
    .wrapper {
    	display:flex;
		justify-content:center;
		align-items:center;
    	width:var(--boardsize); height:var(--boardsize);
    	background:rgba(0,0,0,.6);
    }
}

/*blue wins*/
@include winners(blue);
/*red wins*/
@include winners(red);

/**/
form:valid {
	#no-winner {
		display:block;
	}
}
/* reset */
.actions {
	clear:both;
  margin-bottom:2rem;
	text-align:center;

	button {
		margin-top:1rem;
		padding:0.8rem 2rem;
		border:1px solid #1d1d1d;
		color:#555;
		background:#000;
		font-size:0.9rem;
		cursor:pointer;
		transition:background .3s ease-out, border .3s ease-out;
		&:hover {
			border-color:#303030;
			background:#0a0a0a;
		}
	}
}
              
            
!

JS

              
                /*
Modern browsers that support vw units, css counter, and css variables only!

Highly inspired by Bence Szabó's Pure CSS Connect 4
https://codepen.io/finnhvman/pen/xXpzVN
https://css-tricks.com/roman-empire-made-pure-css-connect-4-possible/
*/
              
            
!
999px

Console