Update comments

widgets/heatmap/heatmap.go

@@ -27,10 +27,10 @@ import (
 	"github.com/mum4k/termdash/widgets/heatmap/internal/axes"
 )
 
-// HeatMap draws heatmap charts.
+// HeatMap draws heat map charts.
 //
 // Heatmap consists of several cells. Each cell represents a value.
-// The larger the value, the darker the color of the cell (From white to black).
+// The larger the value, the darker the color of the cell (from white to black).
 //
 // The two dimensions of the values (cells) array are determined by the length of
 // the XLabels and YLabels arrays respectively.

widgets/heatmap/internal/axes/label.go

@@ -53,12 +53,12 @@ func xLabels(yEnd image.Point, graphWidth int, stringLabels []string, cellWidth
 	return nil, errors.New("not implemented")
 }
 
-// paddedLabelLength calculates the length of the padded label and
+// paddedLabelLength calculates the length of the padded X label and
 // the column index corresponding to the label.
-// For example, the longest label's length is 5, like '12:34', and the cell's width is 3.
-// So in order to better display, every three cells will display a label,
-// the label belongs to the middle column of the three columns,
-// and the padded length is 3*3, which is 9.
+// For example, the longest X label's length is 5, like '12:34', and the cell's width is 3.
+// So in order to better display, every three columns of cells will display a X label,
+// the X label belongs to the middle column of the three columns,
+// and the padded length is 3*3 (cellWidth multiplies the number of columns), which is 9.
 func paddedLabelLength(graphWidth, longest, cellWidth int) (l, index int) {
 	return
 }

widgets/heatmap/options.go

@@ -15,6 +15,7 @@
 package heatmap
 
 import (
+	"errors"
 	"github.com/mum4k/termdash/cell"
 )
 
@@ -36,7 +37,7 @@ type options struct {
 
 // validate validates the provided options.
 func (o *options) validate() error {
-	return nil
+	return errors.New("not implemented")
 }
 
 // newOptions returns a new options instance.