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HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

            
              <svg>
	<defs>
		<circle id='point' r='4'/>
		<path id='arc'/>
		<text id='txt'></text>
	</defs>
	
	<g class='lines--fixed'></g>
	
	<g class='line--moving'>
		<line/>
		<g class='points--ctrl'></g>
	</g>
	
	<g class='points--inters'></g>
	
	<g class='arcs'></g>
</svg>

<section class='inf hidden'>
	<div class='content'>
		<p>When two or more parallel lines (the horizontal dark lines) are crossed by another transversal line (the orange line), the corresponding angles (the ones in matching corners) are equal.</p>
		<p>Drag the red dots to change the transversal line. Double click to switch to the next pair of corners.</p>
	</div>
	<button id='toggle'>info</button>
</section>
            
          
!
            
              $l-fixed-c: #333;
$l-moving-c: #e18728;
$p-ctrl-c: #be4c39;
$p-inters-c: #4ca454;
$a-inters-c: $p-ctrl-c;

html, body, svg { height: 100%; }

html { overflow: hidden; }

body { margin: 0; }

svg {
	display: block;
	width: 100%;
}

line { stroke-wdth: 2; }

.lines--fixed line { stroke: $l-fixed-c; }

.line--moving {
	line { stroke: $l-moving-c; }
	
	use { /* control points at ends of line */
		fill: $p-ctrl-c;
		stroke: rgba($p-ctrl-c, .1);
		stroke-width: 32;
		cursor: move;
		
		&:hover {
			stroke: rgba($p-ctrl-c, .2);
		}
	}
}

.points--inters use { fill: $p-inters-c; }

.arcs {
	use {
		fill: transparent;
		stroke: $a-inters-c;
	}
}

text {
	fill: purple;
	stroke: none;
	font: 900 1em monospace;
}

.inf {
	position: absolute;
	top: 100%; left: 50%;
	padding: 0 .5em;
	min-width: 20em;
	transform: translate(-50%, -100%);
	background: rgba(#111, .85);
	color: #fff;
	font: 1em trebuchet ms, verdana, sans-serif;
	transition: .35s ease-out;
	
	button {
		position: absolute;
		bottom: 100%; left: 50%;
		border: solid 0 transparent;
		transform: translate(-50%);
		background: $l-moving-c;
		font: inherit;
		font-size: 2em;
		cursor: pointer;
		
		&:before, &:after {
			position: absolute;
			z-index: -1;
			top: 0; bottom: 0;
			width: 1em;
			background: inherit;
			content: '';
		}
		&:before {
			right: 100%;
			border-radius: 33% 0 0 0;
			transform: skewX(-15deg) translate(25%);
		}
		&:after {
			left: 100%;
			border-radius: 0 33% 0 0;
			transform: skewX(15deg) translate(-25%);
		}
	}
}

.hidden {
	transform: translate(-50%, 0);
}
            
          
!
            
              Object.getOwnPropertyNames(Math).map(function(p) {
	window[p] = Math[p];
});

var rand = function(b, a, is_int) {
	var max = (b === 0 || b) ? b : 1, 
			min = a || 0, 
			gen = a + (b - a)*random();
	
	return (is_int) ? round(gen) : gen;
};

Node.prototype.setAttrs = function(o) {
	for(var p in o) {
		this.setAttribute(p, o[p]);
	}
};

var N = 2 /* no of fixed parallel lines */, 
		ARC_F = 8, 
		J = 1.75, 
		K = .1, 
		NS_URI = 'http://www.w3.org/2000/svg', 
    XLink_NS = 'http://www.w3.org/1999/xlink', 
		
		svg = document.querySelector('svg'), 
		w, h, 
		
		/* definition for point */
		defp = document.getElementById('point'), 
		/* definition for arc */
		defa = document.getElementById('arc'), 
		/* definition for text */
		deft = document.getElementById('txt'), 
		pt_r, lim, arc_r, yunit, 
		
		/* wrapper for fixed lines */
		wf = svg.querySelector('.lines--fixed'), 
		/* wrapper for moving line end poins */
		we = svg.querySelector('.points--ctrl'), 
		/* wrapper for inters points */
		wi = svg.querySelector('.points--inters'), 
		/* wrapper for arcs */
		wa = svg.querySelector('.arcs'), 
		
		populated = false, 
		
		el_lines_fixed = [], 
		el_pts_ctrl = [], 
		el_line_moving = 
			svg.querySelector('.line--moving line'), 
		el_pts_inters = [], 
		el_arcs = [], 
		el_txts = [], 
		
		lines_fixed = [], 
		line_moving, 
		
		dragged = null, 
		quad = 0, p, q, 
		
		itoggle = document.getElementById('toggle');

var Point = function(x, y, el) {
	this.x = (x === 0 || x) ? x : rand(w, 0, 1);
	this.y = (y === 0 || y) ? y : rand(h, 0, 1);
	this.el = el;
	this.changed = true;
		
	this.test = function() {
		return this.el && this.el.tagName && 
			this.el.tagName.toLowerCase() === 'use';
	};
	
	this.change = function(x, y) {
		if(x === 0 || x) { this.x = x; }
		if(y === 0 || y) { this.y = y; }
		
		this.el.setAttrs({
			'x': this.x, 
			'y': this.y
		});
		
		this.changed = true;
	};
	
	this.init = function() {
		if(this.test()) {
			this.change();
		}
	};
	
	this.init();
};

var Line = function(p1, p2, el) {
	this.p1 = p1 || new Point;
	this.p2 = p2 || new Point;
	this.el = el;
	this.rel = [];
	this.n = 0;
	
	this.test = function() {
		return this.el && this.el.tagName && 
			this.el.tagName.toLowerCase() === 'line';
	};
	
	this.intersection = function(line) {
		var dxa = this.p1.x - this.p2.x, 
				dya = this.p1.y - this.p2.y, 
				dxb = line.p1.x - line.p2.x, 
				dyb = line.p1.y - line.p2.y, 
				dma = this.p1.x*this.p2.y - 
							this.p1.y*this.p2.x, 
				dmb = line.p1.x*line.p2.y - 
							line.p1.y*line.p2.x,  
				den = dxa*dyb - dya*dxb, 
				nx = dma*dxb - dxa*dmb, 
				ny = dma*dyb - dya*dmb;
		
		return {
			'x': round(nx/den), 
			'y': round(ny/den)
		};
	};
	
	this.angle = function() {
		var dy = this.p1.y - this.p2.y, 
				dx = this.p1.x - this.p2.x;
		
		return atan2(dy, dx);
	};
	
	this.arcPath = function(alpha) {
		var d_txt = '', x, y, xf, yf, 
				beta = q*PI;
		
		alpha += (p^q)*PI;
				
		x = round(arc_r*cos(alpha));
		y = round(arc_r*sin(alpha));
		xf = round(arc_r*cos(beta));
		yf = round(arc_r*sin(beta));
						
		d_txt = 'M' + x + ',' + y + 
						'A' + arc_r + ' ' + arc_r + ' 0 0 ' + (~~!p) + ' ' + 
						xf + ' ' + yf;
				
		return d_txt;
	};
	
	this.textPos = function(_deg, dims) {
		var bw = dims.width, bh = dims.height, tt, 
				_deg = p?(_deg + 180):_deg, 
				df = pow(-1, q);
				
		tt = 'translate(' + (-bw/2) + ' ' + bh/2 + ')' + 
		 	 	'rotate(' + _deg/2 + ')' + 
		 	 	'translate(' + df*(arc_r + bw/2 + 5) + ')' + 
		 	 	'rotate(' + _deg/-2 + ')';

		return tt;
	};
	
	this.updateRel = function() {
		var coord = {}, x, y, 
				alpha = this.angle(), 
				_deg = round(alpha*180/PI), bb;
		
		defa.setAttrs({'d': this.arcPath(alpha) });
		deft.textContent = (p?(180 - abs(_deg)):abs(_deg)) + '°';
		
		for(var i = 0; i < this.n; i++) {
			coord = this.intersection(this.rel[i].line);
			this.rel[i].inters.change(coord.x, coord.y);
			
			this.rel[i].arc.change();
			
			if(i === 0) {
				bb = this.rel[i].arc.txt.getBBox();
			}
		}
		
		deft.setAttrs({'transform': this.textPos(_deg, bb)});
	};
	
	this.queueChange = function(o, i) {
		if(this['p' + i].changed) {
			o['x' + i] = this['p' + i].x;
			o['y' + i] = this['p' + i].y;
			
			this['p' + i].changed = false;
		}
	};
	
	this.change = function() {
		var to_apply = {};
		
		this.queueChange(to_apply, 1);
		this.queueChange(to_apply, 2);
		
		this.el.setAttrs(to_apply);
		
		if(this.n > 0) {
			this.updateRel();
		}
	};
	
	this.init = function() {
		if(this.test()) {
			this.change();
		}
	};
	
	this.init();
};

var Arc = function(p1, p2, p3, el, txt) {
	this.p1 = p1 || new Point;
	this.p2 = p2 || new Point;
	this.p3 = p3 || new Point;
	this.el = el;
	this.txt = txt;
	
	this.test = function() {
		return this.el && this.el.tagName && 
			this.el.tagName.toLowerCase() === 'use';
	};
	
	this.change = function(alpha) {
		this.el.setAttrs({
			'x': this.p2.x, 
			'y': this.p2.y
		});
		this.txt.setAttrs({
			'x': this.p2.x, 
			'y': this.p2.y
		});
	};
};

var populate = function(wrapper, n, type, def, o) {
	var frag = document.createDocumentFragment(), 
			curr, a = [];
	
	for(var i = 0; i < n; i++) {
		curr = document.createElementNS(NS_URI, type);
		
		if(type === 'use' && def) {
			curr.setAttributeNS(
				XLink_NS, 
				'xlink:href', 
				'#' + def
			);
		}
		
		if(o) {
			curr.setAttrs({ 'id': o + i });
		}
		
		a.push(curr);
		frag.appendChild(curr);
	}
	
	wrapper.appendChild(frag);
	
	return a;
};

var init = function() {
	var s = getComputedStyle(svg), vb, fy, 
			x1, y1, x2, y2, coord = {};
	
	pt_r = ~~defp.getAttribute('r');
	
	lines_fixed = [];
	p = quad%2;
	q = floor(quad/2);
	
	w = ~~s.width.split('px')[0];
	h = ~~s.height.split('px')[0];
	
	vb = [0, 0, w, h];
	
	svg.setAttribute('viewBox', vb.join(' '));
	
	if(!populated) {
		el_lines_fixed = 
			populate(wf, N, 'line');
		el_pts_ctrl = 
			populate(we, 2, 'use', 'point', 'drag');
		el_pts_inters = 
			populate(wi, N, 'use', 'point');
		el_arcs = 
			populate(wa, N, 'use', 'arc');
		el_txts = 
			populate(wa, N, 'use', 'txt');
		
		populated = true;
	}
	
	yunit = ~~(h/(N + 1));
	arc_r = ARC_F*pt_r;
	lim = J*arc_r;
		
	/* moving line */
	x1 = rand((1 - K)*w, K*w, 1);
	y1 = rand(yunit - lim, pt_r, 1);
	x2 = rand((1 - K)*w, K*w, 1);
	y2 = rand(h - pt_r, N*yunit + lim, 1);
	
	line_moving = new Line(
		new Point(x1, y1, el_pts_ctrl[0]), 
		new Point(x2, y2, el_pts_ctrl[1]), 
		el_line_moving
	);
	
	for(var i = 0; i < N; i++) {
		fy = (i + 1)*yunit;
		
		lines_fixed.push(new Line(
			new Point(0, fy), 
			new Point(w, fy), 
			el_lines_fixed[i]
		));
		
		line_moving.rel.push({
			'line': lines_fixed[i],
			'inters': new Point(0,0,el_pts_inters[i]), 
			'arc': null
		});
		
		line_moving.rel[i].arc = new Arc(
			line_moving.p1, 
			line_moving.rel[i].inters, 
			lines_fixed[i].p2, 
			el_arcs[i], 
			el_txts[i]
		);
		
		line_moving.n++;
	}
	
	line_moving.updateRel();
};

init();

addEventListener('resize', init, false);

addEventListener('mousedown', function(e) {
	var t = e.target, cidx;
	
	if(t.id && t.id.indexOf('drag') !== -1) {
		cidx = ~~t.id.split('drag')[1];
		dragged = line_moving['p' + (cidx + 1)];
	}
	console.log(dragged, t, t.id);
}, false);

addEventListener('mousemove', function(e) {
	var x, y;
	
	if(dragged) {		
		x = min(max(e.clientX, K*w), (1 - K)*w);
		y = e.clientY;
		
		if(dragged.el.id.indexOf('0') !== -1) {
			y = max(min(e.clientY, yunit - lim), pt_r);
		}
		if(dragged.el.id.indexOf('1') !== -1) {
			y = min(max(e.clientY, N*yunit + lim), h - pt_r);
		}
		
		dragged.change(x, y);
		line_moving.change();
	}
}, false);

addEventListener('mouseup', function(e) {
	if(dragged) {
		dragged = null;
	}
}, false);

addEventListener('dblclick', function() {
	quad = (quad + 1)%4;
	p = quad%2;
	q = floor(quad/2);
	
	line_moving.updateRel();
}, false);

itoggle.addEventListener('click', function() {
	this.parentNode.classList.toggle('hidden');
}, false);
            
          
!
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