fix joining lines

js/app.js

@@ -49,6 +49,21 @@ function rotatePoint(px, py, angle){
     return [x, y];
 }
 
+function linePoints(e){
+    var x1=e.num('cx'), y1=e.num('cy'), x2=e.num('x2')+x1, y2=e.num('y2')+y1;
+    return [[x1, y1], [x2, y2]];
+}
+
+function pointsAdjacent(p1, p2){
+    return (abs(p1[0] - p2[0]) < 5) && (abs(p1[1] - p2[1]) < 5);
+}
+
+function endpointsMatch(line1, line2){
+    var l1 = linePoints(line1);
+    var l2 = linePoints(line2);
+    return pointsAdjacent(l1[0], l2[0]) || pointsAdjacent(l1[0], l2[1]) || pointsAdjacent(l1[1], l2[0]) || pointsAdjacent(l1[1], l2[0]);
+}
+
 function randomId() {
     // Based on Paul Irish's random hex color:http://www.paulirish.com/2009/random-hex-color-code-snippets/
     // Theoretically could return non-unique values, not going to let that keep me up at night
@@ -312,7 +327,7 @@ Snap.plugin(function (Snap, Element, Paper, global, Fragment) {
         var selfType = this.attr('type');
         var otherType = e.attr('type');
         if (selfType === 'line' && otherType === 'line'){
-            return !! Snap.path.intersection(this, e).length;
+            return (!! Snap.path.intersection(this, e).length) || endpointsMatch(this, e);
         }else if (selfType === 'line'){
             var x1=this.num('cx'), x2=this.num('x2')+x1, y1=this.num('cy'), y2=this.num('y2')+y1;
             var ex=e.num('cx'), ey=e.num('cy');

js/levels.js

@@ -19,10 +19,10 @@ var levels = [
 			['spiral', 0, -75, 25, 500, 3],
 			['spiral', 0, 0, 25, 20, .75],
 
-			['line', 75, -150, 25, 25],
-			['line', 75, -75, 25, 0],
-			['line', 75, 0, 25, -25],
-			['line', 75, 75, 0, 25],
+			['line', 75, -150, 27, 27],
+			['line', 75, -75, 27, 0],
+			['line', 75, 0, 27, -27],
+			['line', 75, 75, 0, 27],
 
 		]
 	},
@@ -32,4 +32,4 @@ var levels = [
 			['line', -25, 0, 100, 0]
 		]
 	},
-]
+]