diff --git a/stack.go b/stack.go
index 1b471de..dd1898b 100644
--- a/stack.go
+++ b/stack.go
@@ -8,8 +8,8 @@ const DefaultSize = 1200
 
 // Stack is a limited FIFO for holding sparkline values.
 type Stack struct {
-	Values []int
-	Len    int
+	values []int
+	len    int
 }
 
 // NewStack inits new Stack with default size limit.
@@ -20,26 +20,26 @@ func NewStack() *Stack {
 // NewStackWithSize inits new Stack with size limit.
 func NewStackWithSize(size int) *Stack {
 	return &Stack{
-		Values: make([]int, size),
-		Len:    size,
+		values: make([]int, size),
+		len:    size,
 	}
 }
 
 // Push inserts data to stack, preserving constant length.
 func (s *Stack) Push(v IntVar) {
 	val := v.Value()
-	s.Values = append(s.Values, val)
-	if len(s.Values) > s.Len {
+	s.values = append(s.values, val)
+	if len(s.values) > s.len {
 		// TODO: check if underlying array is growing constantly
-		s.Values = s.Values[1:]
+		s.values = s.values[1:]
 	}
 }
 
-// IntValues returns stack values explicitly casted to int.
+// Values returns stack values explicitly casted to int.
 //
 // Main case is to use with termui.Sparklines.
-func (s *Stack) IntValues() []int {
-	return s.Values
+func (s *Stack) Values() []int {
+	return s.values
 }
 
 // TODO: implement trim and resize
diff --git a/stack_test.go b/stack_test.go
index 7c773cb..e15a547 100644
--- a/stack_test.go
+++ b/stack_test.go
@@ -2,27 +2,13 @@ package main
 
 import "testing"
 
-func TestPushWithFloatAndIntValue(t *testing.T) {
-	s := NewStack()
-	s.Push(Var(int64(0.0))) // from service.go:guessValue
-	s.Push(Var(5.0))
-	s.Push(Var(float64(15.0)))
-	if _, ok := s.Max.(float64); !ok {
-		t.Fatalf("Expected Max to be float64, but it's not")
-	}
-	s.Push(Var(int64(25.0)))
-	if _, ok := s.Max.(int64); !ok {
-		t.Fatalf("Expected Max to be int64, but it's not")
-	}
-}
-
 func TestStack(t *testing.T) {
 	size := 10
 	s := NewStackWithSize(size)
 
 	for i := 0; i < size+5; i++ {
-		s.Push(i)
-		l := len(s.Values)
+		s.Push(&Number{float64(i)})
+		l := len(s.values)
 
 		if l < size {
 			if l != i+1 {
@@ -35,33 +21,8 @@ func TestStack(t *testing.T) {
 		}
 	}
 
-	if s.Front().(int) != 14 {
-		t.Fatalf("Front returns wrong value: expecting %d, got %d", 14, s.Front())
-	}
-
-	s1 := NewStackWithSize(3)
-	s1.Push(true)
-	s1.Push(false)
-	s1.Push(true)
-
-	ints1 := s1.IntValues()
-	if len(ints1) != 3 {
-		t.Fatalf("expecting len of to be %d, but got %d", 3, len(ints1))
-	}
-	if ints1[0] != 1 || ints1[1] != 0 || ints1[2] != 1 {
-		t.Fatalf("bool values converted to int incorrectly: %v", ints1)
-	}
-
-	s2 := NewStackWithSize(3)
-	s2.Push(0.1)
-	s2.Push(0.5)
-	s2.Push(0.03)
-
-	ints2 := s2.IntValues()
-	if len(ints2) != 3 {
-		t.Fatalf("expecting len to be %d, but got %d", 3, len(ints2))
-	}
-	if ints2[0] != 10 || ints2[1] != 50 || ints2[2] != 3 {
-		t.Fatalf("float values converted to int incorrectly: %v", ints2)
+	got := s.Values()[9]
+	if got != 14 {
+		t.Fatalf("Front returns wrong value: expecting %d, got %d", 14, got)
 	}
 }
diff --git a/ui_multi.go b/ui_multi.go
index 81b8230..7b56eea 100644
--- a/ui_multi.go
+++ b/ui_multi.go
@@ -120,7 +120,7 @@ func (t *TermUI) Update(data UIData) {
 			data.Stats[name].Update(v)
 			max := data.Stats[name].Max().String()
 			t.Sparkline1.Lines[i].Title = fmt.Sprintf("%s (max: %s)", service.Name, max)
-			t.Sparkline1.Lines[i].Data = data.Stacks[name].IntValues()
+			t.Sparkline1.Lines[i].Data = data.Stacks[name].Values()
 		}
 
 		if len(data.Vars) == 1 {
@@ -134,7 +134,7 @@ func (t *TermUI) Update(data UIData) {
 			data.Stats[name].Update(v)
 			max := data.Stats[name].Max().String()
 			t.Sparkline2.Lines[i].Title = fmt.Sprintf("%s (max: %s)", service.Name, max)
-			t.Sparkline2.Lines[i].Data = data.Stacks[name].IntValues()
+			t.Sparkline2.Lines[i].Data = data.Stacks[name].Values()
 		}
 	}
 
diff --git a/ui_single.go b/ui_single.go
index 1eb8c93..615a1c2 100644
--- a/ui_single.go
+++ b/ui_single.go
@@ -106,7 +106,7 @@ func (t *TermUISingle) Update(data UIData) {
 		spl.TitleColor = colorByKind(name.Kind())
 		spl.LineColor = colorByKind(name.Kind())
 
-		spl.Data = data.Stacks[name].IntValues()
+		spl.Data = data.Stacks[name].Values()
 	}
 
 	t.Relayout()
diff --git a/var.go b/var.go
index cf8c788..f69bb29 100644
--- a/var.go
+++ b/var.go
@@ -34,8 +34,10 @@ type IntVar interface {
 	Value() int
 }
 
+// Number is a type for numeric values, obtained from JSON.
+// In JSON it's always float64, so there is no straightforward way
+// to separate float from int, so let's keep everything as float.
 type Number struct {
-	// TODO: add mutex here or level above, in service?
 	val float64
 }
 
@@ -58,6 +60,7 @@ func (v *Number) Value() int {
 	return int(v.val)
 }
 
+// Memory represents memory information in bytes.
 type Memory struct {
 	bytes int64
 }
@@ -80,6 +83,7 @@ func (v *Memory) Value() int {
 	return int(v.bytes)
 }
 
+// Duration represents duration data (in ns)
 type Duration struct {
 	dur time.Duration
 }
@@ -105,6 +109,7 @@ func (v *Duration) Value() int {
 	return int(v.dur)
 }
 
+// Strings represents string data.
 type String struct {
 	str string
 }