diff --git a/index.html b/index.html
index 517e0c1..af5fee9 100644
--- a/index.html
+++ b/index.html
@@ -65,9 +65,9 @@ A Voronoi diagram is supposed to be here but for some reason it cannot be displa
 	<br>
 
 	<label for="inputHeat">Heat:&nbsp;</label>
-	<input id="inputHeat" type="number" value="50" step="1" size="10">
+	<input id="inputHeat" type="number" value="50" step="1" size="10" min="-1e7" max="1e7">
 	<label for="inputHumidity">Humidity:&nbsp;</label>
-	<input id="inputHumidity" type="number" value="50" step="1" size="10">
+	<input id="inputHumidity" type="number" value="50" step="1" size="10" min="-1e7" max="1e7">
 
 	<br>
 
@@ -110,29 +110,29 @@ A Voronoi diagram is supposed to be here but for some reason it cannot be displa
 <form id="noiseForm">
 	<h3>Heat (<code>mg_biome_np_heat</code>)</h3>
 	<label for="inputNoiseHeatOffset">Offset:&nbsp;</label>
-	<input id="inputNoiseHeatOffset" type="number" value="50" size="10">
+	<input id="inputNoiseHeatOffset" type="number" value="50" size="10" min="-1e7" max="1e7">
 
 	<label for="inputNoiseHeatScale">Scale:&nbsp;</label>
-	<input id="inputNoiseHeatScale" type="number" value="50" size="10">
+	<input id="inputNoiseHeatScale" type="number" value="50" size="10" min="-1e7" max="1e7">
 
 	<label for="inputNoiseHeatOctaves">Octaves:&nbsp;</label>
 	<input id="inputNoiseHeatOctaves" type="number" value="3" step="1" min="1" max="65535" size="10">
 
 	<label for="inputNoiseHeatPersistence">Persistence:&nbsp;</label>
-	<input id="inputNoiseHeatPersistence" type="number" value="0.5" step=0.1 size="10">
+	<input id="inputNoiseHeatPersistence" type="number" value="0.5" step=0.1 size="10" min="-1e7" max="1e7">
 
 	<h3>Humidity (<code>mg_biome_np_humidity</code>)</h3>
 	<label for="inputNoiseHumidityOffset">Offset:&nbsp;</label>
-	<input id="inputNoiseHumidityOffset" type="number" value="50" size="10">
+	<input id="inputNoiseHumidityOffset" type="number" value="50" size="10" min="-1e7" max="1e7">
 
 	<label for="inputNoiseHumidityScale">Scale:&nbsp;</label>
-	<input id="inputNoiseHumidityScale" type="number" value="50" size="10">
+	<input id="inputNoiseHumidityScale" type="number" value="50" size="10" min="-1e7" max="1e7">
 
 	<label for="inputNoiseHumidityOctaves">Octaves:&nbsp;</label>
 	<input id="inputNoiseHumidityOctaves" type="number" value="3" step="1" min="1" max="65535" size="10">
 
 	<label for="inputNoiseHumidityPersistence">Persistence:&nbsp;</label>
-	<input id="inputNoiseHumidityPersistence" type="number" value="0.5" step=0.1 size="10">
+	<input id="inputNoiseHumidityPersistence" type="number" value="0.5" step=0.1 size="10" min="-1e7" max="1e7">
 
 	<h3>Reset</h3>
 	<button id="inputNoiseReset" type="button">Reset noise parameters</button>
diff --git a/mibpov.js b/mibpov.js
index 6487e21..1ab1aad 100644
--- a/mibpov.js
+++ b/mibpov.js
@@ -16,6 +16,10 @@ const MIN_CANVAS_SIZE = 100;
 // Minimum required distance of canvas from the right page side
 const CANVAS_PAGE_MARGIN_RIGHT = 20
 
+// Minimum and maximum value for heat and humidity
+const MIN_HEAT_HUMIDITY_VALUE = -1e7
+const MAX_HEAT_HUMIDITY_VALUE = 1e7
+
 // Grid widths. We use lower grid widths
 // as the grid becomes more crammed.
 // There are 4 levels from 0 to 3.
@@ -101,6 +105,9 @@ let draw_humidity_min, draw_humidity_max;
 let midpoint_heat;
 let midpoint_humidity;
 
+// Y altitude at which the diagram is currently viewed at
+let viewY = 0;
+
 // Biome noise settings
 const NOISE_OFFSET_DEFAULT = 50;
 const NOISE_SCALE_DEFAULT = 50;
@@ -259,12 +266,9 @@ function addBiome(biomeDef) {
 	draw(true);
 }
 
-// Get the Y vale of the widget to set the Y altitude
+// Get the Y value of the viewed altitude
 function getViewY() {
-	if (!inputViewY) {
-		return 0;
-	}
-	return inputViewY.value;
+	return viewY;
 }
 // Returns the biome point by its given ID
 // or null if it couldn't be found
@@ -843,6 +847,14 @@ function draw(recalculate) {
 		return true;
 	}
 
+	// Render a special message if the value range is huge
+	if ((limit_heat_max - limit_heat_min > MAX_HEAT_HUMIDITY_VALUE) || (limit_humidity_max - limit_humidity_min > MAX_HEAT_HUMIDITY_VALUE)) {
+		showDiagramMessage(context, "Value range is too large.");
+		drawError = true;
+		putResizeCorner(context);
+		return true;
+	}
+
 	let points = getRenderedPoints(y);
 	// Render a special message if there are no biomes
 	if (points.length === 0) {
@@ -1256,7 +1268,7 @@ function updatePointWhenDragged(pointID) {
 /* Updates the text showing the current altitude (Y height)
 the diagram currently applies */
 function updateAltitudeText() {
-	altitudeDisplay.innerHTML = "showing diagram for altitude Y=<span class='statAltitude'>"+inputViewY.value+"</span>";
+	altitudeDisplay.innerHTML = "showing diagram for altitude Y=<span class='statAltitude'>"+getViewY()+"</span>";
 }
 
 
@@ -1552,8 +1564,12 @@ biomeSelector.onchange = function() {
 
 addBiomeButton.onclick = function() {
 	// Add a biome at a random position
-	let he = Math.round(limit_heat_min + Math.random() * (limit_heat_max - limit_heat_min));
-	let hu = Math.round(limit_humidity_min + Math.random() * (limit_humidity_max - limit_humidity_min));
+	let he_min = Math.max(MIN_HEAT_HUMIDITY_VALUE, limit_heat_min);
+	let he_max = Math.min(MAX_HEAT_HUMIDITY_VALUE, limit_heat_max);
+	let hu_min = Math.max(MIN_HEAT_HUMIDITY_VALUE, limit_heat_min);
+	let hu_max = Math.min(MAX_HEAT_HUMIDITY_VALUE, limit_heat_max);
+	let he = Math.round(he_min + Math.random() * (he_max - he_min));
+	let hu = Math.round(hu_min + Math.random() * (hu_max - hu_min));
 	addBiome({name: generateBiomeName(lastBiomeID), heat: he, humidity: hu, min_y: MIN_Y_DEFAULT, max_y: MAX_Y_DEFAULT});
 }
 removeBiomeButton.onclick = function() {
@@ -1583,18 +1599,28 @@ removeBiomeButton.onclick = function() {
 }
 
 /* Biome editing widgets events */
+function handleBiomeNumberInput(biomeValueName, element) {
+	let val = +element.value;
+	if (element.value === "" || typeof val !== "number") {
+		return;
+	}
+	if (element.min !== "" && (val < +element.min || val > +element.max)) {
+		return;
+	}
+	onChangeBiomeValueWidget(biomeValueName, val);
+}
 
 inputHeat.oninput = function() {
-	onChangeBiomeValueWidget("heat", +this.value);
+	handleBiomeNumberInput("heat", this);
 }
 inputHumidity.oninput = function() {
-	onChangeBiomeValueWidget("humidity", +this.value);
+	handleBiomeNumberInput("humidity", this);
 }
 inputMinY.oninput = function() {
-	onChangeBiomeValueWidget("min_y", +this.value);
+	handleBiomeNumberInput("min_y", this);
 }
 inputMaxY.oninput = function() {
-	onChangeBiomeValueWidget("max_y", +this.value);
+	handleBiomeNumberInput("max_y", this);
 }
 inputBiomeName.oninput = function() {
 	onChangeBiomeValueWidget("name", this.value);
@@ -1603,6 +1629,11 @@ inputBiomeName.oninput = function() {
 /* Diagram view settings events */
 
 inputViewY.oninput = function() {
+	let y = +this.value;
+	if (y === null) {
+		return;
+	}
+	viewY = Math.floor(y);
 	draw(true);
 	updateAltitudeText();
 }
@@ -1629,53 +1660,43 @@ inputCheckboxAxes.onchange = function() {
 
 /* Noise parameters events */
 
-inputNoiseHeatScale.oninput = function() {
-	noises.heat.scale = +this.value;
+function updateNoiseParam(noiseName, noiseValueName, element) {
+	if (element.value === "") {
+		return;
+	}
+	let val = +element.value;
+	if (val < +element.min || val > +element.max) {
+		return;
+	}
+	noises[noiseName][noiseValueName] = val;
 	clear();
 	updateAreaVars();
 	draw(true);
 }
+
+inputNoiseHeatScale.oninput = function() {
+	updateNoiseParam("heat", "scale", this);
+}
 inputNoiseHeatOffset.oninput = function() {
-	noises.heat.offset = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("heat", "offset", this);
 }
 inputNoiseHeatPersistence.oninput = function() {
-	noises.heat.persistence = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("heat", "persistence", this);
 }
 inputNoiseHeatOctaves.oninput = function() {
-	noises.heat.octaves = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("heat", "octaves", this);
 }
 inputNoiseHumidityScale.oninput = function() {
-	noises.humidity.scale = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("humidity", "scale", this);
 }
 inputNoiseHumidityOffset.oninput = function() {
-	noises.humidity.offset = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("humidity", "offset", this);
 }
 inputNoiseHumidityPersistence.oninput = function() {
-	noises.humidity.persistence = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("humidity", "persistence", this);
 }
 inputNoiseHumidityOctaves.oninput = function() {
-	noises.humidity.octaves = +this.value;
-	clear();
-	updateAreaVars();
-	draw(true);
+	updateNoiseParam("humidity", "octaves", this);
 }
 inputNoiseReset.onclick = function() {
 	noises.heat.offset = NOISE_OFFSET_DEFAULT;