diff --git a/web/client.js b/web/client.js
index c314f22..aa8fb1b 100644
--- a/web/client.js
+++ b/web/client.js
@@ -125,12 +125,22 @@ function readModeData(mode, reader)
 function lsb(value) { return value & 0xFF; }
 function msb(value) { return (value >> 8) & 0xFF; }
 
+
+function getBrightness(value)
+{
+  if (typeof(value) == 'string' && value.substr(-1) === '%')
+    return (Number(value.substr(0, value.length - 1)) * 4096 / 100);
+
+  return Number(value) || 0;
+}
+
+
 function writeModeData(mode, data)
 {
   switch (mode)
   {
     case protocol.Mode.Static:
-      if (typeof(data.brightness) == 'undefined') data.brightness = 0;
+      var brightness = getBrightness(data.brightness);
 
       return new Buffer([protocol.Command.SetMode, mode, lsb(data.brightness), msb(data.brightness)]);
 
@@ -143,27 +153,27 @@ function writeModeData(mode, data)
       buffer.writeInt8(mode, 1);
 
       for (var index = 0; index < valueCount; index++)
-        buffer.writeInt16LE(brightness[index], 2 + (index * 2));
+        buffer.writeInt16LE(getBrightness(brightness[index]), 2 + (index * 2));
 
       return buffer;
 
     case protocol.Mode.Alternate:
-      if (typeof(data.brightness) == 'undefined') data.brightness = 0;
+      var brightness = getBrightness(data.brightness);
       if (typeof(data.interval) == 'undefined') data.interval = 500;
 
       return new Buffer([protocol.Command.SetMode, mode,
                          lsb(data.interval), msb(data.interval),
-                         lsb(data.brightness), msb(data.brightness)]);
+                         lsb(brightness), msb(brightness)]);
 
     case protocol.Mode.Slide:
-      if (typeof(data.brightness) == 'undefined') data.brightness = 0;
+      var brightness = getBrightness(data.brightness);
       if (typeof(data.interval) == 'undefined') data.interval = 500;
       if (typeof(data.direction) == 'undefined') data.direction = 0;
       if (typeof(data.fadeOutTime) == 'undefined') data.fadeOutTime = 0;
 
       return new Buffer([protocol.Command.SetMode, mode,
                          lsb(data.interval), msb(data.interval),
-                         lsb(data.brightness), msb(data.brightness),
+                         lsb(brightness), msb(brightness),
                          data.direction,
                          lsb(data.fadeOutTime), msb(data.fadeOutTime)]);
   }