diff --git a/build.sbt b/build.sbt
index adfd79e..7f90eae 100644
--- a/build.sbt
+++ b/build.sbt
@@ -15,7 +15,7 @@ lazy val root = (project in file(".")).
 
     libraryDependencies += "com.sksamuel.scrimage" %% "scrimage-filters" % "2.1.8",
     
-    libraryDependencies += "org.json4s" %% "json4s-jackson" % "3.6.1"
+    libraryDependencies += "org.json4s" %% "json4s-jackson" % "3.6.5"
    
 )
 
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index 69e5af0..60c09c1 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -1,5 +1,5 @@
 import sbt._
 
 object Dependencies {
-  lazy val scalaTest = "org.scalatest" %% "scalatest" % "3.0.3"
+  lazy val scalaTest = "org.scalatest" %% "scalatest" % "3.0.7"
 }
diff --git a/src/main/java/lc/GifSequenceWriter.java b/src/main/java/lc/GifSequenceWriter.java
index 46c2f70..0cf014a 100644
--- a/src/main/java/lc/GifSequenceWriter.java
+++ b/src/main/java/lc/GifSequenceWriter.java
@@ -1,3 +1,6 @@
+// This code was adapted from http://elliot.kroo.net/software/java/GifSequenceWriter/
+// It was available under CC By 3.0
+
 package lc;
 import javax.imageio.*;
 import javax.imageio.metadata.*;
@@ -139,13 +142,4 @@ public class GifSequenceWriter {
         rootNode.appendChild(node);
         return(node);
     }
-
-    /**
-     public GifSequenceWriter(
-     BufferedOutputStream outputStream,
-     int imageType,
-     int timeBetweenFramesMS,
-     boolean loopContinuously) {
-
-     */
 }
diff --git a/src/main/scala/lc/RainDropsCaptcha.scala b/src/main/scala/lc/RainDropsCaptcha.scala
new file mode 100644
index 0000000..0b79add
--- /dev/null
+++ b/src/main/scala/lc/RainDropsCaptcha.scala
@@ -0,0 +1,124 @@
+package lc
+
+import java.awt.image.BufferedImage
+import java.awt.RenderingHints
+import java.awt.Font
+import java.awt.font.TextAttribute
+import java.awt.Color
+import java.io.ByteArrayOutputStream
+import javax.imageio.ImageIO
+import javax.imageio.stream.ImageOutputStream;
+import javax.imageio.stream.MemoryCacheImageOutputStream;
+
+class Drop {
+  var x = 0
+  var y = 0
+  var yOffset = 0
+  var color = 0
+  var colorChange = 10
+  def mkColor = {
+    new Color(color, color,  math.min(200, color+100))
+  }
+}
+
+class RainDropsCP extends ChallengeProvider {
+  private val alphabet = "abcdefghijklmnopqrstuvwxyz"
+  private val n = 6
+  private val bgColor = new Color(200, 200, 200)
+  private val textColor = new Color(208, 208, 218)
+  private val textHighlightColor = new Color(100, 100, 125)
+
+  def getId = "FilterChallenge"
+
+  private def extendDrops(drops: Array[Drop], steps: Int, xOffset: Int) = {
+    drops.map(d => {
+      val nd = new Drop()
+      nd.x + xOffset*steps
+      nd.y + d.yOffset*steps
+      nd
+    })
+  }
+
+  def returnChallenge(): Challenge = {
+    val r = new scala.util.Random
+    val secret = Stream.continually(r.nextInt(alphabet.size)).map(alphabet).take(n).mkString
+    val width = 450
+    val height = 100
+    val imgType = BufferedImage.TYPE_INT_RGB
+    val xOffset = 2+r.nextInt(3)
+    val xBias = (height / 10) - 2
+    val dropsOrig = Array.fill[Drop](2000)( new Drop())
+    for (d <- dropsOrig) {
+      d.x = r.nextInt(width) - (xBias/2)*xOffset
+      d.yOffset = 6+r.nextInt(6)
+      d.y = r.nextInt(height)
+      d.color = r.nextInt(240)
+      if (d.color > 128) {
+        d.colorChange *= -1
+      }
+    }
+    val drops = dropsOrig ++ extendDrops(dropsOrig, 1, xOffset) ++ extendDrops(dropsOrig, 2, xOffset) ++ extendDrops(dropsOrig, 3, xOffset)
+
+
+    val baseFont = new Font(Font.MONOSPACED, Font.BOLD, 80)
+    val attributes = new java.util.HashMap[TextAttribute, Object]()
+    attributes.put(TextAttribute.TRACKING, Double.box(0.2))
+    attributes.put(TextAttribute.WEIGHT, TextAttribute.WEIGHT_EXTRABOLD)
+    val spacedFont = baseFont.deriveFont(attributes)
+
+    val baos = new ByteArrayOutputStream();
+    val ios = new MemoryCacheImageOutputStream(baos);
+    val writer = new GifSequenceWriter(ios, imgType, 60, true);
+    for(i <- 0 until 60){
+      // val yOffset = 5+r.nextInt(5)
+      val canvas = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB)
+      val g = canvas.createGraphics()
+      g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)
+
+      // clear the canvas
+      g.setColor(bgColor)
+      g.fillRect(0, 0, canvas.getWidth, canvas.getHeight)
+
+      // paint the rain
+      for (d <- drops) {
+        g.setColor(d.mkColor)
+        g.drawLine(d.x, d.y, d.x+xOffset, d.y+d.yOffset)
+        d.x += xOffset/2
+        d.y += d.yOffset/2
+        d.color += d.colorChange
+        if (d.x > width || d.y > height) {
+          val ySteps =  (height / d.yOffset) + 1
+          d.x -= xOffset*ySteps
+          d.y -= d.yOffset*ySteps
+
+        }
+        if (d.color > 200 || d.color < 21) {
+          d.colorChange *= -1
+        }
+      }
+
+      // center the text
+      g.setFont(spacedFont)
+      val textWidth = g.getFontMetrics().charsWidth(secret.toCharArray, 0, secret.toCharArray.length)
+      val textX = (width - textWidth)/2
+
+      // paint the top outline
+      g.setColor(textHighlightColor)
+      g.drawString(secret, textX, 69)
+      // paint the text
+      g.setColor(textColor)
+      g.drawString(secret, textX, 70)
+
+      g.dispose()
+      writer.writeToSequence(canvas)
+    }
+    writer.close
+    ios.close
+
+    // ImageIO.write(canvas,"png",baos);
+    new Challenge(baos.toByteArray, "image/png", secret)
+  }
+  def checkAnswer(secret: String, answer: String): Boolean = {
+    secret == answer
+  }
+}