         else
             throw "color mode "+m+" is not supported"
 
-    darken: (amount=0.2) ->
+    darker: (amount=20) ->
         me = @
         lch = me.lch()
-        lch[2] -= amount
+        lch[0] -= amount
         chroma.lch lch
+
+    brighter: (amount=20) ->
+        @darker -amount
+
+    saturate: (amount=20) ->
+        me = @
+        lch = me.lch()
+        lch[1] += amount
+        chroma.lch lch
+
+    desaturate: (amount=20) ->
+        @saturate -amount
+
 
 
 hex2rgb = (hex) ->


    hsi: ->
        rgb2hsi @_rgb

    interpolate: (f, col, m) ->
        ###

        if chroma.colors? and chroma.colors[hex]
            hex = chroma.colors[hex]
        else
            throw "unknown color: "+hex
    if hex.length == 4 or hex.length == 7
        hex = hex.substr(1)
    if hex.length == 3
