diff --git a/example/sequenceViewer.html b/example/sequenceViewer.html
index 9cc2ec3..aceaadd 100644
--- a/example/sequenceViewer.html
+++ b/example/sequenceViewer.html
@@ -11,5 +11,8 @@
         .nrows(2)
         .startPos([0, 3])
         .seq(seqs)
+        .palette(["#b3ff99", "#ff9999", "#99b3ff", "#ffe699"])
+        .colourDomain(["A", "T", "C", "G"]) //this probably should go to the charttype itself... At some point
+        .mode("canvas")
 		.place("#container");		
 </script>
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diff --git a/src/sequenceViewer.js b/src/sequenceViewer.js
index 6d5fcaa..1c4ea75 100644
--- a/src/sequenceViewer.js
+++ b/src/sequenceViewer.js
@@ -5,30 +5,111 @@ export function sequenceViewer() {
     const chart = heatmap()
         .add_property("seq", undefined, check("array_fun", "seq"))
         .add_property("reverseComplement", false)
-        .add_property("startPos", 0, check(("array_fun", "seq")));
-    
+        .add_property("startPos", 0, check(("array_fun", "seq")))
+        .add_property("highlightMatches", true);     
+
     //number of rows is defined by heatmap logic
     //number of cols must be defined based on all the sequences and start postions
 
     chart
         .value((i, j) => chart.get_seq(i)[j - chart.get_startPos(i)])
         .ncols(function() {
-            var ncol = 0;
-            for(let i = 0; i < chart.nrows(); i++) {
-                ncol = d3.max([ncol, chart.get_startPos(i) + chart.get_seq(i).length]);
+            var ncol = 0,
+                rowIds = chart.rowIds();
+            for(let i = 0; i < rowIds.length; i++) {
+                ncol = d3.max([ncol, chart.get_startPos(rowIds[i]) + chart.get_seq(rowIds[i]).length]);
             }
             return ncol;
         })
-        .showLegend(false)
+        //.showLegend(false)
         .showValue(true)
         .plotHeight(() => chart.nrows() * 30)
         .informText(function(rowId, colId) {
 			var value = chart.get_value(rowId, colId);
-            console.log(chart.get_startPos(rowId))
 			return "Sequence: <b>" + chart.get_rowLabel(rowId) + "</b>;<br>" + 
 					    "Position: <b>" + (colId - chart.get_startPos(rowId) + 1) + "</b>;<br>" + 
 						"nucleotide = " + value;
 			})
+        .set_paddings({"top": 60});
+    
+    var inherited_updateCellColour = chart.updateCellColour;
+    chart.updateCellColour = function() {
+        inherited_updateCellColour();
+        chart.g.selectAll(".data_element")
+            .attr("stroke", "black")
+        chart.updateCellStroke();
+    }
+
+    chart.updateCellStroke = function(){
+        if(!chart.checkMode())
+            return chart;
+        if(get_mode() == "svg") {
+            if(chart.transitionDuration() > 0 && !chart.transitionOff)
+                chart.g.selectAll(".data_element").transition("cellStroke").duration(chart.transitionDuration())
+                    .attr("stroke-width", function(d) {
+                        let val = chart.get_value(d[0], d[1]),
+                            matching = isMatching(d[1]);
+                        d3.select(this)
+                            .classed("matching", matching);
+                        return val !== undefined && matching ? 2 : 0;
+                    })
+            else
+                chart.g.selectAll(".data_element")
+                    .attr("stroke-width", function(d) {
+                        let val = chart.get_value(d[0], d[1]),
+                            matching = isMatching(d[1]);
+                        d3.select(this)
+                            .classed("matching", matching);
+                        return val !== undefined && matching ? 2 : 0;
+                    })
+            chart.g
+                .selectAll(".data_element.matching")
+                .raise();                    
+        } else {
+            var ctx = chart.canvas.node().getContext("2d");
+            ctx.strokeStyle = "black";
+            ctx.lineWidth = 2;
+            var rowIds = chart.dispRowIds(),
+			    colIds = chart.dispColIds(),
+			    ncols = colIds.length, nrows = rowIds.length;
+            for(let j = 0; j < ncols; j++) 
+                if(isMatching(colIds[j])) {
+                    var x = chart.axes.scale_x(chart.get_heatmapCol(colIds[j]));
+                    for(let i = 0; i < nrows; i++)
+                        if(chart.get_value(rowIds[i], colIds[j]) !== undefined) {
+                            var y = chart.axes.scale_y(chart.get_heatmapRow(rowIds[i]))
+                            ctx.strokeRect(x, y, chart.cellSize.width, chart.cellSize.height);
+                        }
+                }
+                            
+        }
+        return chart;
+    }
+
+	function get_mode() {
+		if(chart.mode() == "default")
+			return chart.dispColIds().length * chart.dispRowIds().length > 2500 ? "canvas" : "svg";
+		return chart.mode();
+	}
+    function isMatching(colId) {
+        var matching = true,
+            rowIds = chart.rowIds(),
+            i = 0, count = 1,
+            val, newVal;
+        while (matching && i < rowIds.length){
+            if(val === undefined) {
+                val = chart.get_value(rowIds[i], colId);
+            } else {
+                newVal = chart.get_value(rowIds[i], colId);
+                if(newVal !== undefined) {
+                    count++;
+                    matching = val == newVal
+                }
+            }
+            i++;
+        }
+        return matching && count > 1;
+    };
     
     return chart;
 }
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