diff --git a/scss.inc.php b/scss.inc.php
index d8b667bd..9feac84b 100644
--- a/scss.inc.php
+++ b/scss.inc.php
@@ -25,7 +25,6 @@ class scssc {
 		"function" => "^",
 	);
 
-	static protected $numberPrecision = 3;
 	static protected $unitTable = array(
 		"in" => array(
 			"in" => 1,
@@ -71,9 +70,7 @@ function compile($code, $name=null) {
 		$this->compileRoot($tree);
 		$this->flattenSelectors($this->scope);
 
-		ob_start();
-		$this->formatter->block($this->scope);
-		$out = ob_get_clean();
+		$out = $this->formatter->block($this->scope);
 
 		setlocale(LC_NUMERIC, $locale);
 		return $out;
@@ -329,7 +326,7 @@ protected function evalSelectorPart($piece) {
 	protected function compileSelector($selector) {
 		if (!is_array($selector)) return $selector; // media and the like
 
-		return implode(" ", array_map(
+		return $this->formatter->implodeSelectors(array_map(
 			array($this, "compileSelectorPart"), $selector));
 	}
 
@@ -457,7 +454,9 @@ protected function compileChild($child, $out) {
 				$this->compileValue($child[2]));
 			break;
 		case "comment":
-			$out->lines[] = $child[1];
+			if(!$this->formatter->stripComments){
+				$out->lines[] = $child[1];
+			}
 			break;
 		case "mixin":
 		case "function":
@@ -965,21 +964,11 @@ protected function compileValue($value) {
 			$r = round($r);
 			$g = round($g);
 			$b = round($b);
+			$a = (count($value) == 5) ? max(0,min($value[4],1)) : 1;
 
-			if (count($value) == 5 && $value[4] != 1) { // rgba
-				return 'rgba('.$r.', '.$g.', '.$b.', '.$value[4].')';
-			}
-
-			$h = sprintf("#%02x%02x%02x", $r, $g, $b);
-
-			// Converting hex color to short notation (e.g. #003399 to #039)
-			if ($h[1] === $h[2] && $h[3] === $h[4] && $h[5] === $h[6]) {
-				$h = '#' . $h[1] . $h[3] . $h[5];
-			}
-
-			return $h;
+			return $this->formatter->color($r, $g, $b, $a);
 		case "number":
-			return round($value[1], self::$numberPrecision) . $value[2];
+			return $this->formatter->number($value[1],$value[2]);
 		case "string":
 			return $value[1] . $this->compileStringContent($value) . $value[1];
 		case "function":
@@ -993,7 +982,7 @@ protected function compileValue($value) {
 			foreach ($items as &$item) {
 				$item = $this->compileValue($item);
 			}
-			return implode("$delim ", $items);
+			return $this->formatter->implodeList($delim, $items);
 		case "interpolated": # node created by extractInterpolation
 			list(, $interpolate, $left, $right) = $value;
 			list(,, $whiteLeft, $whiteRight) = $interpolate;
@@ -1417,10 +1406,12 @@ protected function coerceColor($value) {
 		switch ($value[0]) {
 		case "color": return $value;
 		case "keyword":
-			$name = $value[1];
+			$name = strtolower($value[1]);
 			if (isset(self::$cssColors[$name])) {
-				list($r, $g, $b) = explode(',', self::$cssColors[$name]);
-				return array('color', $r, $g, $b);
+				$color = explode(',', self::$cssColors[$name]);
+				// array('color', $r, $g, $b);
+				array_unshift($color, 'color');
+				return $color;
 			}
 			return null;
 		}
@@ -2043,7 +2034,8 @@ protected function lib_comparable($args) {
 		return true; // TODO: THIS
 	}
 
-	static protected $cssColors = array(
+	public static $cssColors = array(
+		'transparent' => '0,0,0,0',
 		'aliceblue' => '240,248,255',
 		'antiquewhite' => '250,235,215',
 		'aqua' => '0,255,255',
@@ -3515,6 +3507,13 @@ class scss_formatter {
 	public $close = "}";
 	public $tagSeparator = ", ";
 	public $assignSeparator = ": ";
+	
+	public $removeTrailingSemicolon = false;
+	public $replaceColorNames = false;
+	public $omitZeroUnit = false;
+	public $omitZeroLeading = false;
+	public $stripComments = false;
+	public $numberPrecision = 3;
 
 	public function __construct() {
 		$this->indentLevel = 0;
@@ -3528,13 +3527,64 @@ public function property($name, $value) {
 		return $name . $this->assignSeparator . $value . ";";
 	}
 
+	public function implodeList($delim, $items) {
+	    return implode("$delim ", $items);
+	}
+
+	public function implodeSelectors($selectors) {
+	    return implode(" ", $selectors);
+	}
+
+	public function color($r, $g, $b, $a) {
+		if (($a = $this->number($a, null)) != 1) { // rgba
+			if ($a == 0 && $this->replaceColorNames) {
+				return 'transparent';
+			}
+		    return 'rgba('.$r.$this->tagSeparator.$g.$this->tagSeparator.$b.$this->tagSeparator.$a.')';
+		}
+		
+		$h = sprintf("#%02x%02x%02x", $r, $g, $b);
+		
+		// Converting hex color to short notation (e.g. #003399 to #039)
+		if ($h[1] === $h[2] && $h[3] === $h[4] && $h[5] === $h[6]) {
+		    $h = '#' . $h[1] . $h[3] . $h[5];
+		}
+		
+		if ($this->replaceColorNames) {
+		    // Convert hex color to css color name if shorter (e.g. #f00 to red)
+		    $name = array_search($r.','.$g.','.$b, scssc::$cssColors, true);
+		    if ($name !== false && strlen($name) < strlen($h)) {
+		        $h = $name;
+		    }
+		}
+		
+		return $h;
+	}
+	
+	public function number($num, $unit) {
+		$num = round($num, $this->numberPrecision);
+		if ($this->omitZeroUnit && $num == 0) {
+		    return 0;
+		}
+		if ($this->omitZeroLeading) {
+		    if ($num > 0 && $num < 1) {
+		        $num = substr($num, 1);
+		    } else if ($num < 0 && $num > -1) {
+		        $num = '-' . substr($num, 2);
+		    }
+		}
+		return $num . $unit;
+	}
+
 	public function block($block) {
-		if (empty($block->lines) && empty($block->children)) return;
+		if (empty($block->lines) && empty($block->children)) return '';
 
 		$inner = $pre = $this->indentStr();
+		
+		$ret = '';
 
 		if (!empty($block->selectors)) {
-			echo $pre .
+			$ret .= $pre .
 				implode($this->tagSeparator, $block->selectors) .
 				$this->open . $this->break;
 			$this->indentLevel++;
@@ -3543,21 +3593,25 @@ public function block($block) {
 
 		if (!empty($block->lines)) {
 			$glue = $this->break.$inner;
-			echo $inner . implode($glue, $block->lines);
+			$ret .= $inner . implode($glue, $block->lines);
+
 			if (!empty($block->children)) {
-				echo $this->break;
+				$ret .= $this->break;
+			} else if ($this->removeTrailingSemicolon && substr($ret, -1) === ';') {
+			    $ret = substr($ret, 0, -1);
 			}
 		}
 
 		foreach ($block->children as $child) {
-			$this->block($child);
+			$ret .= $this->block($child);
 		}
 
 		if (!empty($block->selectors)) {
 			$this->indentLevel--;
-			if (empty($block->children)) echo $this->break;
-			echo $pre . $this->close . $this->break;
+			if (empty($block->children)) $ret .= $this->break;
+			$ret .= $pre . $this->close . $this->break;
 		}
+		return $ret;
 	}
 }
 
@@ -3591,10 +3645,12 @@ public function block($block) {
 		if ($block->type == "root") {
 			$this->adjustAllChildren($block);
 		}
+		
+		$ret = '';
 
 		$inner = $pre = $this->indentStr($block->depth - 1);
 		if (!empty($block->selectors)) {
-			echo $pre .
+			$ret .= $pre .
 				implode($this->tagSeparator, $block->selectors) .
 				$this->open . $this->break;
 			$this->indentLevel++;
@@ -3603,20 +3659,25 @@ public function block($block) {
 
 		if (!empty($block->lines)) {
 			$glue = $this->break.$inner;
-			echo $inner . implode($glue, $block->lines);
-			if (!empty($block->children)) echo $this->break;
+			$ret .= $inner . implode($glue, $block->lines);
+
+			if (!empty($block->children)) {
+				$ret .= $this->break;
+			} else if ($this->removeTrailingSemicolon && substr($ret, -1) === ';') {
+			    $ret = substr($ret, 0, -1);
+			}
 		}
 
 		foreach ($block->children as $i => $child) {
 			// echo "*** block: ".$block->depth." child: ".$child->depth."\n";
-			$this->block($child);
+			$ret .= $this->block($child);
 			if ($i < count($block->children) - 1) {
-				echo $this->break;
+				$ret .= $this->break;
 
 				if (isset($block->children[$i + 1])) {
 					$next = $block->children[$i + 1];
 					if ($next->depth == max($block->depth, 1) && $child->depth >= $next->depth) {
-						echo $this->break;
+						$ret .= $this->break;
 					}
 				}
 			}
@@ -3624,12 +3685,13 @@ public function block($block) {
 
 		if (!empty($block->selectors)) {
 			$this->indentLevel--;
-			echo $this->close;
+			$ret .= $this->close;
 		}
 
 		if ($block->type == "root") {
-			echo $this->break;
+			$ret .= $this->break;
 		}
+		return $ret;
 	}
 }
 
@@ -3638,10 +3700,42 @@ class scss_formatter_compressed extends scss_formatter {
 	public $tagSeparator = ",";
 	public $assignSeparator = ":";
 	public $break = "";
+	public $removeTrailingSemicolon = true;
+	public $replaceColorNames = true;
+	public $omitZeroUnit = true;
+	public $omitZeroLeading = true;
+	public $stripComments = true;
 
 	public function indentStr($n = 0) {
 		return "";
 	}
+
+	public function implodeList($delim, $list) {
+	    // no delimiter => actually a whitespace separated list (as in "margin")
+	    if ($delim == "") {
+	        $delim = " ";
+	    }
+	    return implode($delim, $list);
+	}
+
+	public function implodeSelectors($selectors){
+	    $ret = '';
+	    $ws = false;
+	    foreach($selectors as $selector){
+	        // do not use whitespace around descendant selectors
+	        if (in_array($selector,array('+','~','>'),true)) {
+	            $ws = false;
+	        }else{
+	            if ($ws) {
+	                $ret .= ' ';
+	            } else {
+	                $ws = true;
+	            }
+	        }
+	        $ret .= $selector;
+	    }
+	    return $ret;
+	}
 }
 
 class scss_server {
diff --git a/tests/ApiTest.php b/tests/ApiTest.php
index b4406784..333d23e6 100644
--- a/tests/ApiTest.php
+++ b/tests/ApiTest.php
@@ -14,14 +14,14 @@ public function testUserFunction() {
 		});
 
 		$this->assertEquals(
-			$this->compile("result: add-two(10, 20);"),
-			"result: 30;");
+			"result: 30;",
+			$this->compile("result: add-two(10, 20);"));
 	}
 	
 	public function testImportMissing(){
 		$this->assertEquals(
-			$this->compile('@import "missing";'),
-			'@import "missing";');
+			'@import "missing";',
+			$this->compile('@import "missing";'));
 	}
 	
 	public function testImportCustomCallback(){
@@ -30,8 +30,8 @@ public function testImportCustomCallback(){
 		});
 		
 		$this->assertEquals(
-			$this->compile('@import "variables.css";'),
-			trim(file_get_contents(__DIR__.'/outputs/variables.css')));
+			trim(file_get_contents(__DIR__.'/outputs/variables.css')),
+			$this->compile('@import "variables.css";'));
 	}
 
 	public function compile($str) {
diff --git a/tests/CompressTest.php b/tests/CompressTest.php
new file mode 100644
index 00000000..82f638fc
--- /dev/null
+++ b/tests/CompressTest.php
@@ -0,0 +1,120 @@
+<?php
+
+require_once __DIR__ . "/../scss.inc.php";
+
+class CompressTest extends PHPUnit_Framework_TestCase {
+	public function setUp() {
+		$this->scss = new scssc();
+		$this->scss->setFormatter(new scss_formatter_compressed());
+	}
+
+	public function testCompressTwice(){
+		$code = file_get_contents(__DIR__.'/inputs/variables.scss');
+		
+		$result = $this->scss->compile($code);
+		
+		$this->assertEquals($result,$this->scss->compile($result));
+	}
+
+	public function testCompressFormat(){
+		// check removing trailing semicolons
+		$this->assertEquals('@import "missing";a{border:0;content:";";border:0}b{border:0}',$this->scss->compile('@import "missing";a{border:0;content:";";border:0;}b{border:0;}'));
+		
+		// check removing excessive whitespace
+		$this->assertEquals('body,a,a:hover{border:0}',$this->scss->compile('body, a,  a:hover  { border: 0 ; }'));
+		
+		// check removing empty blocks and comments
+		$this->assertEquals('a{display:hidden}',$this->scss->compile('  /* comment */  b{a{ }} strong{;;;} a{display:hidden;;;} b{/*inner comment*/}'));
+		
+		// do not mess around with attribute selectors
+		// http://www.w3.org/TR/CSS2/selector.html#attribute-selectors
+		$this->assertEquals('input[type="image"][disabled]{opacity:.5}',$this->scss->compile(' input[type="image"][disabled] { opacity: 0.5; } '));
+		
+		// remove optional whitespace for child selectors, but keep whitespace for descendant selectors
+		// http://www.w3.org/TR/CSS2/selector.html#child-selectors
+		$this->assertEquals('a+b,c>d,e f{display:none}a.b>c d:not(.e){border:0}',$this->scss->compile('  a  +  b  ,  c  >  d  ,  e  f  { display: none; } a.b > c d:not(.e) { border: 0; }'));
+		
+		// remove whitespace around list delimiter, but keep whitespace between space separated values
+		$this->assertEquals('*{a:red,green,blue}a{margin:0 0 0 0}',$this->scss->compile('* { a: red, green , blue ; } a { margin:  0  0  0   0; }'));
+	}
+
+	/**
+	 * @dataProvider equalMediaProvider
+	 */
+	public function testMediaQueries($in,$out){
+		$this->assertEquals('@media '.$out.'{a{border:0}}',$this->scss->compile('@media '.$in.' {a{border:0}}'));
+	}
+
+	public function equalMediaProvider() {
+		// http://www.w3.org/TR/css3-mediaqueries/
+		return $this->prepareSet(array(
+			'only screen' => 'only screen', // unchanged
+			'  only  screen ' => 'only screen', // remove optional whitespace
+ 			'screen, print' => 'screen,print', // remove whitespace between OR'ed queries
+			'(min-width:  100px )' => '(min-width:100px)', // check media features
+			'(min-width: 0px)' => '(min-width:0)', // remove zero unit
+			'only screen and (min-width:  0px) and (max-width: 1000px)' => 'only screen and (min-width:0) and (max-width:1000px)',
+ 			'handheld, only screen and (max-width: 1000px)' => 'handheld,only screen and (max-width:1000px)',
+ 			'screen and (device-aspect-ratio: 16/9) , print and (min-resolution: 300dpi)' => 'screen and (device-aspect-ratio:16/9),print and (min-resolution:300dpi)'
+		));
+	}
+
+	/**
+	 * @dataProvider equalColorsProvider
+	 */
+	public function testCompressColor($in,$out) {
+		$this->assertEquals('color:'.$out,$this->scss->compile('color:'.$in));
+	}
+
+	public function equalColorsProvider() {
+		return $this->prepareSet(array(
+			'red' => 'red', // unchanged color keyword as shortest
+			'#000' => '#000', // unchanged short hex
+			'#00ff00' => '#0f0', // short hex
+			'#7abAaA' => '#7abaaa', // always use lowercase hex
+			'rgb(255,255,255)' => '#fff', // short hex
+			'rgb(123,121,121)' => '#7b7979', // hex instead of RGB notation
+			'rgb( 0 , 0 , 255 )' => '#00f', // short hex for excessive whitespace
+			'rgba(123,121,121,1)' => '#7b7979', // full alpha => use hex
+			'rgba(123,121,121,2)' => '#7b7979', // cap excessive alpha to full alpha
+			'rgba(123,121,121,0.9999)' => '#7b7979', // round alpha component
+			'rgba(123,121,121,0.5)' => 'rgba(123,121,121,.5)', // remove useless leading zero
+			'rgba(123,121,121,0)' => 'transparent', // zero alpha => shorthand transparent color keyword
+			'opacify(transparent, 1)' => '#000', // fully opaque 'transparent' is actually black
+			'opacify(transparent, 0.3)' => 'rgba(0,0,0,.3)', // work with transparent color keyword
+			'opacify(WhiTe,1)' => '#fff' // color keywords are actually case insensitive
+		));
+	}
+
+	/**
+	 * @dataProvider equalNumbersProvider
+	 */
+	public function testCompressNumber($in,$out){
+		$this->assertEquals('padding:'.$out,$this->scss->compile('padding:'.$in));
+	}
+
+	public function equalNumbersProvider(){
+		return $this->prepareSet(array(
+			'14px' => '14px', // unchanged
+			'0px'  => '0', // remove zero unit
+			'0em'  => '0',
+			'0%'   => '0',
+			'1.5em' => '1.5em',
+			'0.5em' => '.5em', // remove leading zero
+			'0.50pt' => '.5pt', // remove leading and trailing zero and keep unit
+			'-4.0'	=> '-4', // remove useless fraction
+			'4.000px' => '4px',
+			'4.9999' => '5', // round to next number
+			'4.99'   => '4.99',
+			'-0.2pt' => '-.2pt', // remove leading zero for negative numbers
+			'-0pt'	 => '0', // negative zero is still zero
+			'+4%'	 => '4%', // remove useless postive number marker
+			'+0em'	 => '0'
+		));
+	}
+	
+	private function prepareSet($set){
+		return array_map(function($in, $out) { return array($in, $out); }, array_keys($set), $set);
+	}
+
+}