diff --git a/MetaballsKit/Metaballs.swift b/MetaballsKit/Metaballs.swift
index 4cdb5eb..6ce2bb2 100644
--- a/MetaballsKit/Metaballs.swift
+++ b/MetaballsKit/Metaballs.swift
@@ -293,6 +293,17 @@ public class Field {
             didChange = true
         }
 
+        if let target = userInfo["target"] as? Float {
+            parameters.target = target
+            defaults.target = target
+            didChange = true
+        }
+        if let feather = userInfo["feather"] as? Float {
+            parameters.feather = feather
+            defaults.feather = feather
+            didChange = true
+        }
+
         if didChange {
             populateParametersBuffer()
         }
diff --git a/MetaballsKit/Preferences.swift b/MetaballsKit/Preferences.swift
index 24a90d6..4ac90cd 100644
--- a/MetaballsKit/Preferences.swift
+++ b/MetaballsKit/Preferences.swift
@@ -9,6 +9,36 @@
 import Cocoa
 
 extension UserDefaults {
+    public var target: Float {
+        get {
+            if let obj = object(forKey: "target") as? NSNumber {
+                return obj.floatValue
+            } else {
+                let defaultValue: Float = 1.0
+                set(defaultValue, forKey: "target")
+                return defaultValue
+            }
+        }
+        set {
+            set(newValue, forKey: "target")
+        }
+    }
+
+    public var feather: Float {
+        get {
+            if let obj = object(forKey: "feather") as? NSNumber {
+                return obj.floatValue
+            } else {
+                let defaultValue: Float = 0.25
+                set(defaultValue, forKey: "target")
+                return defaultValue
+            }
+        }
+        set {
+            set(newValue, forKey: "feather")
+        }
+    }
+
     public var colorStyle: ColorStyle? {
         get {
             let value = integer(forKey: "colorStyle")
diff --git a/MetaballsKit/PreferencesViewController.swift b/MetaballsKit/PreferencesViewController.swift
index 1d536f4..c4c1c36 100644
--- a/MetaballsKit/PreferencesViewController.swift
+++ b/MetaballsKit/PreferencesViewController.swift
@@ -39,6 +39,34 @@ public class PreferencesViewController: NSViewController {
     private var colorStackView = NSStackView()
     private var colorViews = [ColorView]()
 
+    private lazy var targetSlider: SliderView = {
+        let targetSlider = SliderView(label: NSLocalizedString("Target", comment: "name of the target slider"))
+        targetSlider.slider.tag = Slider.target.rawValue
+        if #available(OSX 10.12.2, *) {
+            targetSlider.slider.trackFillColor = nil
+        }
+        targetSlider.slider.minValue = 0
+        targetSlider.slider.maxValue = 1
+        targetSlider.slider.target = self
+        targetSlider.slider.action = #selector(PreferencesViewController.sliderDidUpdate(sender:))
+        targetSlider.slider.floatValue = self.defaults.target
+        return targetSlider
+    }()
+
+    private lazy var featherSlider: SliderView = {
+        let featherSlider = SliderView(label: NSLocalizedString("Feather", comment: "name of the feather slider"))
+        featherSlider.slider.tag = Slider.feather.rawValue
+        if #available(OSX 10.12.2, *) {
+            featherSlider.slider.trackFillColor = nil
+        }
+        featherSlider.slider.minValue = 0
+        featherSlider.slider.maxValue = 1
+        featherSlider.slider.target = self
+        featherSlider.slider.action = #selector(PreferencesViewController.sliderDidUpdate(sender:))
+        featherSlider.slider.floatValue = self.defaults.feather
+        return featherSlider
+    }()
+
     private lazy var styleMenu: NSPopUpButton = {
         let button = NSPopUpButton()
         button.translatesAutoresizingMaskIntoConstraints = false
@@ -100,13 +128,15 @@ public class PreferencesViewController: NSViewController {
 
         colorStackView.addArrangedSubview(styleMenu)
         for i in 0..<4 {
-            let colorView = ColorView()
+            let colorView = ColorView(label: "Color \(i+1)")
             colorView.translatesAutoresizingMaskIntoConstraints = false
-            colorView.label.stringValue = "Color \(i+1)"
             colorStackView.addArrangedSubview(colorView)
             colorViews.append(colorView)
         }
 
+        colorStackView.addArrangedSubview(targetSlider)
+        colorStackView.addArrangedSubview(featherSlider)
+
         showCloseButtonIfNeeded()
 
         self.view = view
@@ -163,6 +193,10 @@ public class PreferencesViewController: NSViewController {
         postColorNotification()
     }
 
+    func sliderDidUpdate(sender: NSSlider) {
+        postColorNotification()
+    }
+
     func closeWindow() {
         self.view.window?.close()
     }
@@ -191,23 +225,30 @@ public class PreferencesViewController: NSViewController {
         for (idx, cv) in colorViews.enumerated() {
             info["color\(idx)"] = cv.colorWell.color
         }
+        info["target"] = targetSlider.slider.floatValue
+        info["feather"] = featherSlider.slider.floatValue
         NotificationCenter.default.post(name: PreferencesDidChange_Color, object: nil, userInfo: info)
     }
 }
 
-class ColorView: NSView {
+class ParameterView: NSView {
     private let stackView = NSStackView()
-    internal let colorWell = NSColorWell()
-    internal let label = NSTextField(labelWithString: "Hello")
+    internal let control: NSControl
+    internal let label: NSTextField
 
-    override init(frame frameRect: NSRect) {
-        super.init(frame: frameRect)
+    init(frame f: NSRect, control c: NSControl, label: String = "Hello") {
+        control = c
+        self.label = NSTextField(labelWithString: label)
+        super.init(frame: f)
         commonInit()
     }
 
+    convenience init(control c: NSControl) {
+        self.init(frame: NSRect(), control: c)
+    }
+    
     required init?(coder: NSCoder) {
-        super.init(coder: coder)
-        commonInit()
+        fatalError("init(coder:) has not been implemented")
     }
 
     private func commonInit() {
@@ -217,9 +258,9 @@ class ColorView: NSView {
         stackView.alignment = .centerY
         stackView.distribution = .equalSpacing
 
-        colorWell.translatesAutoresizingMaskIntoConstraints = false
-        colorWell.setContentHuggingPriority(251, for: .horizontal)
-        stackView.addArrangedSubview(colorWell)
+        control.translatesAutoresizingMaskIntoConstraints = false
+        control.setContentHuggingPriority(251, for: .horizontal)
+        stackView.addArrangedSubview(control)
 
         label.translatesAutoresizingMaskIntoConstraints = false
         stackView.addArrangedSubview(label)
@@ -233,3 +274,31 @@ class ColorView: NSView {
         ])
     }
 }
+
+class ColorView: ParameterView {
+    var colorWell: NSColorWell {
+        return control as! NSColorWell
+    }
+
+    init(label: String) {
+        super.init(frame: NSRect(), control: NSColorWell(), label: label)
+    }
+
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
+
+class SliderView: ParameterView {
+    var slider: NSSlider {
+        return control as! NSSlider
+    }
+
+    init(label: String) {
+        super.init(frame: NSRect(), control: NSSlider(), label: label)
+    }
+
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+}
diff --git a/MetaballsKit/Shaders.metal b/MetaballsKit/Shaders.metal
index 3294bda..a49bbcc 100644
--- a/MetaballsKit/Shaders.metal
+++ b/MetaballsKit/Shaders.metal
@@ -64,8 +64,8 @@ passthroughVertexShader(uint vid                    [[vertex_id]],
 float sampleAtPoint(float2, constant Ball*, int);
 
 // Color samplers
-float4 singleColor(float, float, float4);
-float4 gradient2(float, float, float, float4, float4);
+float4 singleColor(float, float, float, float4);
+float4 gradient2(float, float, float, float, float4, float4);
 
 // Helpers
 float mapValueFromRangeOntoRange(float, float, float, float, float);
@@ -76,17 +76,18 @@ sampleToColorShader(RasterizerData in               [[stage_in]],
                     constant Parameters& parameters [[buffer(0)]],
                     constant Ball* balls            [[buffer(1)]])
 {
-    const float target = 1.0;
+    const float target = parameters.target;
+    const float feather = parameters.feather;
     const float sample = sampleAtPoint(in.position.xy, balls, parameters.numberOfBalls);
     const float blend = in.position.x / parameters.size.x;
 
     float4 out;
     switch (parameters.colorStyle) {
         case SingleColor:
-            out = singleColor(sample, target, parameters.colors[0]);
+            out = singleColor(sample, target, feather, parameters.colors[0]);
             break;
         case Gradient2Horizontal:
-            out = gradient2(sample, target, blend, parameters.colors[0], parameters.colors[1]);
+            out = gradient2(sample, target, feather, blend, parameters.colors[0], parameters.colors[1]);
             break;
     }
 
@@ -112,15 +113,17 @@ sampleAtPoint(float2 point,
 float4
 singleColor(float sample,
             float target,
+            float feather,
             float4 color)
 {
     float4 out;
-    if (sample > 1.0) {
+    if (sample > target) {
         out = color;
     }
 
     // Feather the alpha value.
-    const float a = clamp(mapValueFromRangeOntoRange(sample, 0.75 * target, target, 0, 1), 0.0, 1.0);
+    const float mappedAlpha = mapValueFromRangeOntoRange(sample, (1.0 - feather) * target, target, 0, 1);
+    const float a = clamp(mappedAlpha, 0.0, 1.0);
     out = float4(out.xyz, a);
 
     return out;
@@ -129,12 +132,13 @@ singleColor(float sample,
 float4
 gradient2(float sample,
           float target,
+          float feather,
           float normalizedBlend,
           float4 fromColor,
           float4 toColor)
 {
     float4 blendedColor = averageTwoColors(normalizedBlend, fromColor, toColor);
-    float4 out = singleColor(sample, target, blendedColor);
+    float4 out = singleColor(sample, target, feather, blendedColor);
     return out;
 }