diff --git a/js/rtree/rbush.js b/js/rtree/rbush.js
new file mode 100644
index 0000000..8a6492e
--- /dev/null
+++ b/js/rtree/rbush.js
@@ -0,0 +1,626 @@
+/* https://github.com/mourner/rbush*/
+
+(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.rbush = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
+'use strict';
+
+module.exports = rbush;
+
+var quickselect = require('quickselect');
+
+function rbush(maxEntries, format) {
+    if (!(this instanceof rbush)) return new rbush(maxEntries, format);
+
+    // max entries in a node is 9 by default; min node fill is 40% for best performance
+    this._maxEntries = Math.max(4, maxEntries || 9);
+    this._minEntries = Math.max(2, Math.ceil(this._maxEntries * 0.4));
+
+    if (format) {
+        this._initFormat(format);
+    }
+
+    this.clear();
+}
+
+rbush.prototype = {
+
+    all: function () {
+        return this._all(this.data, []);
+    },
+
+    search: function (bbox) {
+
+        var node = this.data,
+            result = [],
+            toBBox = this.toBBox;
+
+        if (!intersects(bbox, node)) return result;
+
+        var nodesToSearch = [],
+            i, len, child, childBBox;
+
+        while (node) {
+            for (i = 0, len = node.children.length; i < len; i++) {
+
+                child = node.children[i];
+                childBBox = node.leaf ? toBBox(child) : child;
+
+                if (intersects(bbox, childBBox)) {
+                    if (node.leaf) result.push(child);
+                    else if (contains(bbox, childBBox)) this._all(child, result);
+                    else nodesToSearch.push(child);
+                }
+            }
+            node = nodesToSearch.pop();
+        }
+
+        return result;
+    },
+
+    collides: function (bbox) {
+
+        var node = this.data,
+            toBBox = this.toBBox;
+
+        if (!intersects(bbox, node)) return false;
+
+        var nodesToSearch = [],
+            i, len, child, childBBox;
+
+        while (node) {
+            for (i = 0, len = node.children.length; i < len; i++) {
+
+                child = node.children[i];
+                childBBox = node.leaf ? toBBox(child) : child;
+
+                if (intersects(bbox, childBBox)) {
+                    if (node.leaf || contains(bbox, childBBox)) return true;
+                    nodesToSearch.push(child);
+                }
+            }
+            node = nodesToSearch.pop();
+        }
+
+        return false;
+    },
+
+    load: function (data) {
+        if (!(data && data.length)) return this;
+
+        if (data.length < this._minEntries) {
+            for (var i = 0, len = data.length; i < len; i++) {
+                this.insert(data[i]);
+            }
+            return this;
+        }
+
+        // recursively build the tree with the given data from stratch using OMT algorithm
+        var node = this._build(data.slice(), 0, data.length - 1, 0);
+
+        if (!this.data.children.length) {
+            // save as is if tree is empty
+            this.data = node;
+
+        } else if (this.data.height === node.height) {
+            // split root if trees have the same height
+            this._splitRoot(this.data, node);
+
+        } else {
+            if (this.data.height < node.height) {
+                // swap trees if inserted one is bigger
+                var tmpNode = this.data;
+                this.data = node;
+                node = tmpNode;
+            }
+
+            // insert the small tree into the large tree at appropriate level
+            this._insert(node, this.data.height - node.height - 1, true);
+        }
+
+        return this;
+    },
+
+    insert: function (item) {
+        if (item) this._insert(item, this.data.height - 1);
+        return this;
+    },
+
+    clear: function () {
+        this.data = createNode([]);
+        return this;
+    },
+
+    remove: function (item, equalsFn) {
+        if (!item) return this;
+
+        var node = this.data,
+            bbox = this.toBBox(item),
+            path = [],
+            indexes = [],
+            i, parent, index, goingUp;
+
+        // depth-first iterative tree traversal
+        while (node || path.length) {
+
+            if (!node) { // go up
+                node = path.pop();
+                parent = path[path.length - 1];
+                i = indexes.pop();
+                goingUp = true;
+            }
+
+            if (node.leaf) { // check current node
+                index = findItem(item, node.children, equalsFn);
+
+                if (index !== -1) {
+                    // item found, remove the item and condense tree upwards
+                    node.children.splice(index, 1);
+                    path.push(node);
+                    this._condense(path);
+                    return this;
+                }
+            }
+
+            if (!goingUp && !node.leaf && contains(node, bbox)) { // go down
+                path.push(node);
+                indexes.push(i);
+                i = 0;
+                parent = node;
+                node = node.children[0];
+
+            } else if (parent) { // go right
+                i++;
+                node = parent.children[i];
+                goingUp = false;
+
+            } else node = null; // nothing found
+        }
+
+        return this;
+    },
+
+    toBBox: function (item) { return item; },
+
+    compareMinX: compareNodeMinX,
+    compareMinY: compareNodeMinY,
+
+    toJSON: function () { return this.data; },
+
+    fromJSON: function (data) {
+        this.data = data;
+        return this;
+    },
+
+    _all: function (node, result) {
+        var nodesToSearch = [];
+        while (node) {
+            if (node.leaf) result.push.apply(result, node.children);
+            else nodesToSearch.push.apply(nodesToSearch, node.children);
+
+            node = nodesToSearch.pop();
+        }
+        return result;
+    },
+
+    _build: function (items, left, right, height) {
+
+        var N = right - left + 1,
+            M = this._maxEntries,
+            node;
+
+        if (N <= M) {
+            // reached leaf level; return leaf
+            node = createNode(items.slice(left, right + 1));
+            calcBBox(node, this.toBBox);
+            return node;
+        }
+
+        if (!height) {
+            // target height of the bulk-loaded tree
+            height = Math.ceil(Math.log(N) / Math.log(M));
+
+            // target number of root entries to maximize storage utilization
+            M = Math.ceil(N / Math.pow(M, height - 1));
+        }
+
+        node = createNode([]);
+        node.leaf = false;
+        node.height = height;
+
+        // split the items into M mostly square tiles
+
+        var N2 = Math.ceil(N / M),
+            N1 = N2 * Math.ceil(Math.sqrt(M)),
+            i, j, right2, right3;
+
+        multiSelect(items, left, right, N1, this.compareMinX);
+
+        for (i = left; i <= right; i += N1) {
+
+            right2 = Math.min(i + N1 - 1, right);
+
+            multiSelect(items, i, right2, N2, this.compareMinY);
+
+            for (j = i; j <= right2; j += N2) {
+
+                right3 = Math.min(j + N2 - 1, right2);
+
+                // pack each entry recursively
+                node.children.push(this._build(items, j, right3, height - 1));
+            }
+        }
+
+        calcBBox(node, this.toBBox);
+
+        return node;
+    },
+
+    _chooseSubtree: function (bbox, node, level, path) {
+
+        var i, len, child, targetNode, area, enlargement, minArea, minEnlargement;
+
+        while (true) {
+            path.push(node);
+
+            if (node.leaf || path.length - 1 === level) break;
+
+            minArea = minEnlargement = Infinity;
+
+            for (i = 0, len = node.children.length; i < len; i++) {
+                child = node.children[i];
+                area = bboxArea(child);
+                enlargement = enlargedArea(bbox, child) - area;
+
+                // choose entry with the least area enlargement
+                if (enlargement < minEnlargement) {
+                    minEnlargement = enlargement;
+                    minArea = area < minArea ? area : minArea;
+                    targetNode = child;
+
+                } else if (enlargement === minEnlargement) {
+                    // otherwise choose one with the smallest area
+                    if (area < minArea) {
+                        minArea = area;
+                        targetNode = child;
+                    }
+                }
+            }
+
+            node = targetNode || node.children[0];
+        }
+
+        return node;
+    },
+
+    _insert: function (item, level, isNode) {
+
+        var toBBox = this.toBBox,
+            bbox = isNode ? item : toBBox(item),
+            insertPath = [];
+
+        // find the best node for accommodating the item, saving all nodes along the path too
+        var node = this._chooseSubtree(bbox, this.data, level, insertPath);
+
+        // put the item into the node
+        node.children.push(item);
+        extend(node, bbox);
+
+        // split on node overflow; propagate upwards if necessary
+        while (level >= 0) {
+            if (insertPath[level].children.length > this._maxEntries) {
+                this._split(insertPath, level);
+                level--;
+            } else break;
+        }
+
+        // adjust bboxes along the insertion path
+        this._adjustParentBBoxes(bbox, insertPath, level);
+    },
+
+    // split overflowed node into two
+    _split: function (insertPath, level) {
+
+        var node = insertPath[level],
+            M = node.children.length,
+            m = this._minEntries;
+
+        this._chooseSplitAxis(node, m, M);
+
+        var splitIndex = this._chooseSplitIndex(node, m, M);
+
+        var newNode = createNode(node.children.splice(splitIndex, node.children.length - splitIndex));
+        newNode.height = node.height;
+        newNode.leaf = node.leaf;
+
+        calcBBox(node, this.toBBox);
+        calcBBox(newNode, this.toBBox);
+
+        if (level) insertPath[level - 1].children.push(newNode);
+        else this._splitRoot(node, newNode);
+    },
+
+    _splitRoot: function (node, newNode) {
+        // split root node
+        this.data = createNode([node, newNode]);
+        this.data.height = node.height + 1;
+        this.data.leaf = false;
+        calcBBox(this.data, this.toBBox);
+    },
+
+    _chooseSplitIndex: function (node, m, M) {
+
+        var i, bbox1, bbox2, overlap, area, minOverlap, minArea, index;
+
+        minOverlap = minArea = Infinity;
+
+        for (i = m; i <= M - m; i++) {
+            bbox1 = distBBox(node, 0, i, this.toBBox);
+            bbox2 = distBBox(node, i, M, this.toBBox);
+
+            overlap = intersectionArea(bbox1, bbox2);
+            area = bboxArea(bbox1) + bboxArea(bbox2);
+
+            // choose distribution with minimum overlap
+            if (overlap < minOverlap) {
+                minOverlap = overlap;
+                index = i;
+
+                minArea = area < minArea ? area : minArea;
+
+            } else if (overlap === minOverlap) {
+                // otherwise choose distribution with minimum area
+                if (area < minArea) {
+                    minArea = area;
+                    index = i;
+                }
+            }
+        }
+
+        return index;
+    },
+
+    // sorts node children by the best axis for split
+    _chooseSplitAxis: function (node, m, M) {
+
+        var compareMinX = node.leaf ? this.compareMinX : compareNodeMinX,
+            compareMinY = node.leaf ? this.compareMinY : compareNodeMinY,
+            xMargin = this._allDistMargin(node, m, M, compareMinX),
+            yMargin = this._allDistMargin(node, m, M, compareMinY);
+
+        // if total distributions margin value is minimal for x, sort by minX,
+        // otherwise it's already sorted by minY
+        if (xMargin < yMargin) node.children.sort(compareMinX);
+    },
+
+    // total margin of all possible split distributions where each node is at least m full
+    _allDistMargin: function (node, m, M, compare) {
+
+        node.children.sort(compare);
+
+        var toBBox = this.toBBox,
+            leftBBox = distBBox(node, 0, m, toBBox),
+            rightBBox = distBBox(node, M - m, M, toBBox),
+            margin = bboxMargin(leftBBox) + bboxMargin(rightBBox),
+            i, child;
+
+        for (i = m; i < M - m; i++) {
+            child = node.children[i];
+            extend(leftBBox, node.leaf ? toBBox(child) : child);
+            margin += bboxMargin(leftBBox);
+        }
+
+        for (i = M - m - 1; i >= m; i--) {
+            child = node.children[i];
+            extend(rightBBox, node.leaf ? toBBox(child) : child);
+            margin += bboxMargin(rightBBox);
+        }
+
+        return margin;
+    },
+
+    _adjustParentBBoxes: function (bbox, path, level) {
+        // adjust bboxes along the given tree path
+        for (var i = level; i >= 0; i--) {
+            extend(path[i], bbox);
+        }
+    },
+
+    _condense: function (path) {
+        // go through the path, removing empty nodes and updating bboxes
+        for (var i = path.length - 1, siblings; i >= 0; i--) {
+            if (path[i].children.length === 0) {
+                if (i > 0) {
+                    siblings = path[i - 1].children;
+                    siblings.splice(siblings.indexOf(path[i]), 1);
+
+                } else this.clear();
+
+            } else calcBBox(path[i], this.toBBox);
+        }
+    },
+
+    _initFormat: function (format) {
+        // data format (minX, minY, maxX, maxY accessors)
+
+        // uses eval-type function compilation instead of just accepting a toBBox function
+        // because the algorithms are very sensitive to sorting functions performance,
+        // so they should be dead simple and without inner calls
+
+        var compareArr = ['return a', ' - b', ';'];
+
+        this.compareMinX = new Function('a', 'b', compareArr.join(format[0]));
+        this.compareMinY = new Function('a', 'b', compareArr.join(format[1]));
+
+        this.toBBox = new Function('a',
+            'return {minX: a' + format[0] +
+            ', minY: a' + format[1] +
+            ', maxX: a' + format[2] +
+            ', maxY: a' + format[3] + '};');
+    }
+};
+
+function findItem(item, items, equalsFn) {
+    if (!equalsFn) return items.indexOf(item);
+
+    for (var i = 0; i < items.length; i++) {
+        if (equalsFn(item, items[i])) return i;
+    }
+    return -1;
+}
+
+// calculate node's bbox from bboxes of its children
+function calcBBox(node, toBBox) {
+    distBBox(node, 0, node.children.length, toBBox, node);
+}
+
+// min bounding rectangle of node children from k to p-1
+function distBBox(node, k, p, toBBox, destNode) {
+    if (!destNode) destNode = createNode(null);
+    destNode.minX = Infinity;
+    destNode.minY = Infinity;
+    destNode.maxX = -Infinity;
+    destNode.maxY = -Infinity;
+
+    for (var i = k, child; i < p; i++) {
+        child = node.children[i];
+        extend(destNode, node.leaf ? toBBox(child) : child);
+    }
+
+    return destNode;
+}
+
+function extend(a, b) {
+    a.minX = Math.min(a.minX, b.minX);
+    a.minY = Math.min(a.minY, b.minY);
+    a.maxX = Math.max(a.maxX, b.maxX);
+    a.maxY = Math.max(a.maxY, b.maxY);
+    return a;
+}
+
+function compareNodeMinX(a, b) { return a.minX - b.minX; }
+function compareNodeMinY(a, b) { return a.minY - b.minY; }
+
+function bboxArea(a)   { return (a.maxX - a.minX) * (a.maxY - a.minY); }
+function bboxMargin(a) { return (a.maxX - a.minX) + (a.maxY - a.minY); }
+
+function enlargedArea(a, b) {
+    return (Math.max(b.maxX, a.maxX) - Math.min(b.minX, a.minX)) *
+           (Math.max(b.maxY, a.maxY) - Math.min(b.minY, a.minY));
+}
+
+function intersectionArea(a, b) {
+    var minX = Math.max(a.minX, b.minX),
+        minY = Math.max(a.minY, b.minY),
+        maxX = Math.min(a.maxX, b.maxX),
+        maxY = Math.min(a.maxY, b.maxY);
+
+    return Math.max(0, maxX - minX) *
+           Math.max(0, maxY - minY);
+}
+
+function contains(a, b) {
+    return a.minX <= b.minX &&
+           a.minY <= b.minY &&
+           b.maxX <= a.maxX &&
+           b.maxY <= a.maxY;
+}
+
+function intersects(a, b) {
+    return b.minX <= a.maxX &&
+           b.minY <= a.maxY &&
+           b.maxX >= a.minX &&
+           b.maxY >= a.minY;
+}
+
+function createNode(children) {
+    return {
+        children: children,
+        height: 1,
+        leaf: true,
+        minX: Infinity,
+        minY: Infinity,
+        maxX: -Infinity,
+        maxY: -Infinity
+    };
+}
+
+// sort an array so that items come in groups of n unsorted items, with groups sorted between each other;
+// combines selection algorithm with binary divide & conquer approach
+
+function multiSelect(arr, left, right, n, compare) {
+    var stack = [left, right],
+        mid;
+
+    while (stack.length) {
+        right = stack.pop();
+        left = stack.pop();
+
+        if (right - left <= n) continue;
+
+        mid = left + Math.ceil((right - left) / n / 2) * n;
+        quickselect(arr, mid, left, right, compare);
+
+        stack.push(left, mid, mid, right);
+    }
+}
+
+},{"quickselect":2}],2:[function(require,module,exports){
+'use strict';
+
+module.exports = partialSort;
+
+// Floyd-Rivest selection algorithm:
+// Rearrange items so that all items in the [left, k] range are smaller than all items in (k, right];
+// The k-th element will have the (k - left + 1)th smallest value in [left, right]
+
+function partialSort(arr, k, left, right, compare) {
+
+    while (right > left) {
+        if (right - left > 600) {
+            var n = right - left + 1;
+            var m = k - left + 1;
+            var z = Math.log(n);
+            var s = 0.5 * Math.exp(2 * z / 3);
+            var sd = 0.5 * Math.sqrt(z * s * (n - s) / n) * (m - n / 2 < 0 ? -1 : 1);
+            var newLeft = Math.max(left, Math.floor(k - m * s / n + sd));
+            var newRight = Math.min(right, Math.floor(k + (n - m) * s / n + sd));
+            partialSort(arr, k, newLeft, newRight, compare);
+        }
+
+        var t = arr[k];
+        var i = left;
+        var j = right;
+
+        swap(arr, left, k);
+        if (compare(arr[right], t) > 0) swap(arr, left, right);
+
+        while (i < j) {
+            swap(arr, i, j);
+            i++;
+            j--;
+            while (compare(arr[i], t) < 0) i++;
+            while (compare(arr[j], t) > 0) j--;
+        }
+
+        if (compare(arr[left], t) === 0) swap(arr, left, j);
+        else {
+            j++;
+            swap(arr, j, right);
+        }
+
+        if (j <= k) left = j + 1;
+        if (k <= j) right = j - 1;
+    }
+}
+
+function swap(arr, i, j) {
+    var tmp = arr[i];
+    arr[i] = arr[j];
+    arr[j] = tmp;
+}
+
+function defaultCompare(a, b) {
+    return a < b ? -1 : a > b ? 1 : 0;
+}
+
+},{}]},{},[1])(1)
+});