diff --git a/index.html b/index.html
index d64f011..f4ee73b 100644
--- a/index.html
+++ b/index.html
@@ -17,18 +17,6 @@
 				width: 100%;
 				height: 100%;
 			}
-
-			#seamap .seamap-marker .light  {
-				width: 100%;
-				height: 100%;
-				border-radius: 50%;
-				transition: background ease-in-out 50ms;
-				opacity: 0.9;
-			}
-
-			#seamap .seamap-marker .light.on {
-				background: yellow;
-			}
 		</style>
 	</head>
 	<body>
@@ -54,20 +42,22 @@
 			  ?item wdt:P31 wd:Q39715.
 			  ?item wdt:P625 ?location.
 			  OPTIONAL {
-			    ?item wdt:P2048 ?height.
-			    ?item wdt:P2923 ?focalHeight.
-			    ?item wdt:P1030 ?sequence.
+				?item wdt:P2048 ?height.
+				?item wdt:P2923 ?focalHeight.
+				?item wdt:P1030 ?sequence.
 			  }
 			  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
 			}
 		</script>
-		<script src="https://unpkg.com/leaflet@1.2.0/dist/leaflet.js"
-		  integrity="sha512-lInM/apFSqyy1o6s89K4iQUKg6ppXEgsVxT35HbzUupEVRh2Eu9Wdl4tHj7dZO0s1uvplcYGmt3498TtHq+log=="
-		  crossorigin=""></script>
+		<script src="https://unpkg.com/leaflet@1.2.0/dist/leaflet-src.js"></script>
 		<script src="https://unpkg.com/osmtogeojson@3.0.0-beta.2/osmtogeojson.js"
 		  integrity="sha384-O1DMEF/gKYhLsICYtozkRWjEr9OfkZzVawUjyOPtevnKB2S1BegNJO0R251Pfuwz"
 		  crossorigin=""></script>
+		<script src="https://unpkg.com/rbush@2.0.1/rbush.js"></script>
 		<script src="https://unpkg.com/@turf/turf@3.5.2/turf.min.js"></script>
+		<script src="leaflet.indexedfeaturelayer.js"></script>
+		<script src="leaflet.rangedmarker.js"></script>
+		<script src="leaflet.light.js"></script>
 		<script>
 			let map = L.map('seamap').setView([54.2, 2.6], 6);
 			
@@ -84,88 +74,12 @@
 				return [sw.lat, sw.lng, ne.lat, ne.lng]
 			}
 
-			let Light = L.Icon.extend({
-				options: {
-					iconSize: [12, 12],
-					iconAnchor: [6, 6],
-					className: 'seamap-marker',
-					sequence: []
-				},
-
-				createIcon: function(icon) {
-					icon = document.createElement('div');
-
-					this._canvas = document.createElement('div');
-					this._canvas.className = 'light';
-					icon.appendChild(this._canvas);
-
-					this._setIconStyles(icon, 'icon');
-
-					return icon;
-				},
-
-				createShadow: function(icon) {
-					return null;
-				},
-
-				_setIconStyles: function(icon, type) {
-					L.Icon.prototype._setIconStyles.apply(this, arguments);
-				},
-
-				setState: function(state) {
-					this._canvas.classList.toggle('on', !!state);
-				}
-			});
-
-			class Sequence {
-				constructor(seq) {
-					this.setSequence(seq);
-				}
-
-				setSequence(seq) {
-					this.text = seq;
-					
-					this.steps = seq.split('+').map(step => {
-						let state = true;
-						if (/^\(\d+(\.\d+)?\)$/.test(step)) {
-							state = false;
-							step = step.substring(1, step.length - 1);
-						}
-						return [state, parseFloat(step, 10)];
-					});
-
-					this.duration = this.steps.reduce((sum, step) => sum + step[1], 0);
-
-					this.offset = Math.random() * this.duration;
-				}
-
-				isValid() {
-					return this.steps.every(step => !isNaN(step[1]));
-				}
-
-				state(time) {
-					if (isNaN(this.duration))
-						return undefined;
-
-					let dt = (this.offset + time) % this.duration;
-
-					for (let i = 0; i < this.steps.length; ++i) {
-						if (dt < this.steps[i][1])
-							return this.steps[i][0];
-						else
-							dt -= this.steps[i][1];
-					}
-
-					throw new Error('Ran out of steps while still inside duration?');
-				}
-			}
-
 			let query = document.getElementById('seamap-query').textContent
 				.replace(/\{\{bbox\}\}/g, bbox(bounds).join(','));
 
 			let url = 'https://www.overpass-api.de/api/interpreter?data=' + encodeURIComponent(query);
 
-			url = 'data.json'; // For testing
+			url = 'data-full.json'; // For testing
 
 			let data = fetch(url)
 				.then(req => req.json())
@@ -180,23 +94,26 @@
 				}));
 
 			let lights = data.then(geojson => {
-				return L.geoJSON(geojson, {
+				return L.indexedGeoJSON(null, {
 					pointToLayer: function(feat, latlng) {
-						return L.marker(latlng, {
+						return new L.Light(latlng, {
 							interactive: false,
 							title: feat.properties.tags['name'],
-							icon: new Light(),
-							sequence: new Sequence(feat.properties.tags['seamark:light:sequence'])
+							radius: (parseFloat(feat.properties.tags['seamark:light:range'], 10) || 1) * 1000,
+							sequence: new L.Light.Sequence(feat.properties.tags['seamark:light:sequence']),
+							stroke: false,
+							fillOpacity: 0.9,
+							fillColor: '#FF0'
 						});
 					}
-				}).addTo(map);
+				}).addTo(map).addData(geojson);
 			});
 
 			lights.then(layer => {
 				let draw = function(t) {
 					layer.eachLayer(marker => {
 						try {
-							marker.options.icon.setState(marker.options.sequence.state(t));
+							marker.setState(marker.options.sequence.state(t));
 						} catch (e) {
 							console.error(e, marker);
 						}
diff --git a/leaflet.indexedfeaturelayer.js b/leaflet.indexedfeaturelayer.js
new file mode 100644
index 0000000..10f507f
--- /dev/null
+++ b/leaflet.indexedfeaturelayer.js
@@ -0,0 +1,126 @@
+function getBoundsWithPadding(map, padding) {
+	const bounds = map.getPixelBounds(),
+		sw = map.unproject(bounds.getBottomLeft().add([-padding, padding])),
+		ne = map.unproject(bounds.getTopRight().add([padding, -padding]));
+
+	return new L.LatLngBounds(sw, ne);
+}
+
+Object.assign(L.LatLngBounds.prototype, {
+	toMinMax: function() {
+		return {
+			minX: this.getWest(),
+			minY: this.getSouth(),
+			maxX: this.getEast(),
+			maxY: this.getNorth()
+		};
+	}
+});
+
+L.LayerGroup.include({
+	updateLayers: function(layers) {
+		var _layers = {};
+
+		for (var i = 0; i < layers.length; ++i)
+			_layers[this.getLayerId(layers[i])] = layers[i];
+
+		var toRemove = [];
+
+		for (var id in this._layers) {
+			if (!(id in _layers))
+				toRemove.push(this._layers[id]);
+		}
+
+		toRemove.forEach(this.removeLayer, this);
+
+		for (var id in _layers) {
+			if (!(id in this._layers))
+				this.addLayer(_layers[id]);
+		}
+
+		return this;
+	}
+});
+
+L.IndexedFeatureLayer = L.GeoJSON.extend({
+	options: {
+		padding: 30 // in pixels
+	},
+
+	initialize: function (geojson, options) {
+		L.Util.setOptions(this, options);
+
+		this._layers = {};
+
+		this._visible = L.layerGroup([]);
+
+		this._rbush = rbush(9);
+
+		if (geojson) {
+			this.addData(geojson);
+		}
+	},
+
+	search: function(bounds) {
+		return this._rbush.search(bounds.toMinMax()).map(result => result.layer);
+	},
+
+	getLayerId: function(layer) {
+		return layer.feature.id;
+	},
+
+	addLayer: function (layer) {
+		const id = this.getLayerId(layer);
+
+		if (id in this._layers)
+			return this;
+
+		this._layers[id] = layer;
+
+		// Necessary for circle markers I use here
+		layer._map = this._map;
+		layer._project();
+		
+		const xy = layer.getBounds().toMinMax();
+		this._rbush.insert(Object.assign({layer: layer}, xy));
+		
+		if (this._map
+			&& !this._visible.hasLayer(layer)
+			&& this._layerInView(layer)) {
+			layer._map = null;
+			this._visible.addLayer(layer);
+		} else {
+			layer._map = null;
+		}
+
+		return this;
+	},
+
+	onAdd: function (map) {
+		this._visible.addTo(map);
+		map.on('moveend', this._redraw, this);
+		this._redraw();
+	},
+
+	onRemove: function(map) {
+		this._visible.removeFrom(map);
+	},
+
+	_getBounds: function() {
+		return getBoundsWithPadding(this._map, this.options.padding);
+	},
+
+	_redraw: function() {
+		const layers = this.search(this._getBounds());
+		console.log(layers.length, 'layers');
+		this._visible.updateLayers(layers);
+	},
+
+	_layerInView: function(layer) {
+		return layer.getBounds().intersects(this._getBounds());
+	}
+});
+
+L.indexedGeoJSON = function(geojson, options) {
+	return new L.IndexedFeatureLayer(geojson, options);
+};
\ No newline at end of file
diff --git a/leaflet.light.js b/leaflet.light.js
new file mode 100644
index 0000000..0146546
--- /dev/null
+++ b/leaflet.light.js
@@ -0,0 +1,51 @@
+L.Light = L.Circle.extend({
+	setState: function(state) {
+		if (this._state !== state) {
+			L.Path.prototype.setStyle.call(this, {fill: !!state});
+			this._state = state;
+		}
+	}
+});
+
+L.Light.Sequence = class {
+	constructor(seq) {
+		this.setSequence(seq);
+	}
+
+	setSequence(seq) {
+		this.text = seq;
+		
+		this.steps = seq.split('+').map(step => {
+			let state = true;
+			if (/^\(\d+(\.\d+)?\)$/.test(step)) {
+				state = false;
+				step = step.substring(1, step.length - 1);
+			}
+			return [state, parseFloat(step, 10)];
+		});
+
+		this.duration = this.steps.reduce((sum, step) => sum + step[1], 0);
+
+		this.offset = Math.random() * this.duration;
+	}
+
+	isValid() {
+		return this.steps.every(step => !isNaN(step[1]));
+	}
+
+	state(time) {
+		if (isNaN(this.duration))
+			return undefined;
+
+		let dt = (this.offset + time) % this.duration;
+
+		for (let i = 0; i < this.steps.length; ++i) {
+			if (dt < this.steps[i][1])
+				return this.steps[i][0];
+			else
+				dt -= this.steps[i][1];
+		}
+
+		throw new Error('Ran out of steps while still inside duration?');
+	}
+}
\ No newline at end of file
diff --git a/leaflet.rangedmarker.js b/leaflet.rangedmarker.js
new file mode 100644
index 0000000..7709a75
--- /dev/null
+++ b/leaflet.rangedmarker.js
@@ -0,0 +1,39 @@
+L.RangedMarker = L.Marker.extend({
+	options: {
+		range: 1
+	}, 
+	initialize: function(latlng, options) {
+		L.Marker.prototype.initialize.call(this, latlng, options);
+
+		const updateIconSize = this.updateIconSize.bind(this);
+		this.updateCallback = function() {
+			updateIconSize(this);
+		};
+	},
+	onAdd: function(map) {
+		L.Marker.prototype.onAdd.call(this, map);
+		map.on('zoomend', this.updateCallback);
+		this.updateIconSize(map);
+	},
+	onRemove: function(map) {
+		map.off('zoomend', this.updateCallback);
+		L.Marker.prototype.onRemove.call(this, map);
+	},
+	updateIconSize: function(map) {
+		let size = this._getSizeOnMap(map);
+		this._icon.style.width = size + 'px';
+		this._icon.style.height = size + 'px';
+	},
+	_getSizeOnMap: function (map) {
+		return this.options.range / this._getMetersPerPixel(map);
+	},
+	_getMetersPerPixel: function(map) {
+		var centerLatLng = map.getCenter(); // get map center
+		var pointC = map.latLngToContainerPoint(centerLatLng); // convert to containerpoint (pixels)
+		var pointX = L.point(pointC.x + 10, pointC.y); // add 10 pixels to x
+
+		// convert containerpoints to latlng's
+		var latLngX = map.containerPointToLatLng(pointX);
+		return centerLatLng.distanceTo(latLngX) / 10; // calculate distance between c and x (latitude)
+	}
+});
\ No newline at end of file
