diff --git a/android/uhabits-android/src/main/java/org/isoron/uhabits/widgets/HistoryWidget.kt b/android/uhabits-android/src/main/java/org/isoron/uhabits/widgets/HistoryWidget.kt
index 5f69d9b53..353f382f8 100644
--- a/android/uhabits-android/src/main/java/org/isoron/uhabits/widgets/HistoryWidget.kt
+++ b/android/uhabits-android/src/main/java/org/isoron/uhabits/widgets/HistoryWidget.kt
@@ -26,8 +26,8 @@ import org.isoron.platform.gui.AndroidDataView
 import org.isoron.platform.time.JavaLocalDateFormatter
 import org.isoron.uhabits.core.models.Habit
 import org.isoron.uhabits.core.ui.screens.habits.show.views.HistoryCardPresenter
-import org.isoron.uhabits.core.ui.views.DarkTheme
 import org.isoron.uhabits.core.ui.views.HistoryChart
+import org.isoron.uhabits.core.ui.views.WidgetTheme
 import org.isoron.uhabits.core.utils.DateUtils
 import org.isoron.uhabits.widgets.views.GraphWidgetView
 import java.util.Locale
@@ -51,7 +51,7 @@ class HistoryWidget(
             habit = habit,
             isSkipEnabled = prefs.isSkipEnabled,
             firstWeekday = prefs.firstWeekday,
-            theme = DarkTheme(),
+            theme = WidgetTheme(),
         )
         (widgetView.dataView as AndroidDataView).apply {
             (this.view as HistoryChart).series = model.series
@@ -65,7 +65,7 @@ class HistoryWidget(
                 view = HistoryChart(
                     today = DateUtils.getTodayWithOffset().toLocalDate(),
                     paletteColor = habit.color,
-                    theme = DarkTheme(),
+                    theme = WidgetTheme(),
                     dateFormatter = JavaLocalDateFormatter(Locale.getDefault())
                 )
             }
diff --git a/android/uhabits-android/src/main/res/layout/canvas_test.xml b/android/uhabits-android/src/main/res/layout/canvas_test.xml
index 6faa0df2e..41c8c2909 100644
--- a/android/uhabits-android/src/main/res/layout/canvas_test.xml
+++ b/android/uhabits-android/src/main/res/layout/canvas_test.xml
@@ -20,7 +20,8 @@
 
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:orientation="vertical" android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_height="match_parent"
+    android:background="#ffff00">
 
     <org.isoron.platform.gui.AndroidTestView
         android:layout_width="500dp"
diff --git a/android/uhabits-core/assets/test/views/BarChart/themeDark.png b/android/uhabits-core/assets/test/views/BarChart/themeDark.png
new file mode 100644
index 000000000..d9f7f8603
Binary files /dev/null and b/android/uhabits-core/assets/test/views/BarChart/themeDark.png differ
diff --git a/android/uhabits-core/assets/test/views/BarChart/themeWidget.png b/android/uhabits-core/assets/test/views/BarChart/themeWidget.png
new file mode 100644
index 000000000..d044e688c
Binary files /dev/null and b/android/uhabits-core/assets/test/views/BarChart/themeWidget.png differ
diff --git a/android/uhabits-core/assets/test/views/CanvasTest.png b/android/uhabits-core/assets/test/views/CanvasTest.png
index 75b3d8f20..c8e831e6e 100644
Binary files a/android/uhabits-core/assets/test/views/CanvasTest.png and b/android/uhabits-core/assets/test/views/CanvasTest.png differ
diff --git a/android/uhabits-core/assets/test/views/HistoryChart/dark.png b/android/uhabits-core/assets/test/views/HistoryChart/themeDark.png
similarity index 100%
rename from android/uhabits-core/assets/test/views/HistoryChart/dark.png
rename to android/uhabits-core/assets/test/views/HistoryChart/themeDark.png
diff --git a/android/uhabits-core/assets/test/views/HistoryChart/themeWidget.png b/android/uhabits-core/assets/test/views/HistoryChart/themeWidget.png
new file mode 100644
index 000000000..8c39deac3
Binary files /dev/null and b/android/uhabits-core/assets/test/views/HistoryChart/themeWidget.png differ
diff --git a/android/uhabits-core/src/main/java/org/isoron/platform/gui/Canvas.kt b/android/uhabits-core/src/main/java/org/isoron/platform/gui/Canvas.kt
index bd82edbe5..c72417289 100644
--- a/android/uhabits-core/src/main/java/org/isoron/platform/gui/Canvas.kt
+++ b/android/uhabits-core/src/main/java/org/isoron/platform/gui/Canvas.kt
@@ -52,9 +52,16 @@ interface Canvas {
     fun setTextAlign(align: TextAlign)
     fun toImage(): Image
 
+    /**
+     * Fills entire canvas with the current color.
+     */
+    fun fill() {
+        fillRect(0.0, 0.0, getWidth(), getHeight())
+    }
+
     fun drawTestImage() {
-        // Draw grey background
-        setColor(Color(0x303030))
+        // Draw transparent background
+        setColor(Color(0.1, 0.1, 0.1, 0.5))
         fillRect(0.0, 0.0, 500.0, 400.0)
 
         // Draw center rectangle
@@ -63,7 +70,7 @@ interface Canvas {
         drawRect(100.0, 100.0, 300.0, 200.0)
 
         // Draw squares, circles and arcs
-        setColor(Color(0xFFFF00))
+        setColor(Color.YELLOW)
         setStrokeWidth(1.0)
         drawRect(0.0, 0.0, 100.0, 100.0)
         fillCircle(50.0, 50.0, 30.0)
@@ -75,7 +82,7 @@ interface Canvas {
         fillArc(50.0, 350.0, 30.0, 45.0, 90.0)
 
         // Draw two red crossing lines
-        setColor(Color(0xFF0000))
+        setColor(Color.RED)
         setStrokeWidth(2.0)
         drawLine(0.0, 0.0, 500.0, 400.0)
         drawLine(500.0, 0.0, 0.0, 400.0)
@@ -83,7 +90,7 @@ interface Canvas {
         // Draw text
         setFont(Font.BOLD)
         setFontSize(50.0)
-        setColor(Color(0x00FF00))
+        setColor(Color.GREEN)
         setTextAlign(TextAlign.CENTER)
         drawText("HELLO", 250.0, 100.0)
         setTextAlign(TextAlign.RIGHT)
diff --git a/android/uhabits-core/src/main/java/org/isoron/platform/gui/Color.kt b/android/uhabits-core/src/main/java/org/isoron/platform/gui/Color.kt
index 040af1772..a7bd4e770 100644
--- a/android/uhabits-core/src/main/java/org/isoron/platform/gui/Color.kt
+++ b/android/uhabits-core/src/main/java/org/isoron/platform/gui/Color.kt
@@ -23,9 +23,8 @@ data class Color(
     val red: Double,
     val green: Double,
     val blue: Double,
-    val alpha: Double
+    val alpha: Double,
 ) {
-
     val luminosity: Double
         get() {
             return 0.21 * red + 0.72 * green + 0.07 * blue
@@ -53,4 +52,18 @@ data class Color(
         val relativeLuminosity = (l1 + 0.05) / (l2 + 0.05)
         return if (relativeLuminosity >= 1) relativeLuminosity else 1 / relativeLuminosity
     }
+
+    fun withAlpha(newAlpha: Double) = Color(red, green, blue, newAlpha)
+
+    companion object {
+        val TRANSPARENT = Color(0.0, 0.0, 0.0, 0.0)
+        val RED = Color(1.0, 0.0, 0.0, 1.0)
+        val GREEN = Color(0.0, 1.0, 0.0, 1.0)
+        val BLUE = Color(1.0, 0.0, 1.0, 1.0)
+        val YELLOW = Color(1.0, 1.0, 0.0, 1.0)
+        val MAGENTA = Color(1.0, 0.0, 1.0, 1.0)
+        val CYAN = Color(0.0, 1.0, 1.0, 1.0)
+        val WHITE = Color(1.0, 1.0, 1.0, 1.0)
+        val BLACK = Color(0.0, 0.0, 0.0, 1.0)
+    }
 }
diff --git a/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/BarChart.kt b/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/BarChart.kt
index 533b3a69e..c272e937e 100644
--- a/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/BarChart.kt
+++ b/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/BarChart.kt
@@ -49,7 +49,6 @@ class BarChart(
     var barMargin = 3.0
     var barWidth = 12.0
     var nGridlines = 6
-    var backgroundColor = theme.cardBackgroundColor
 
     override val dataColumnWidth: Double
         get() = barWidth + barMargin * 2
@@ -67,8 +66,8 @@ class BarChart(
         var maxValue = series.map { it.max()!! }.max()!!
         maxValue = max(maxValue, 1.0)
 
-        canvas.setColor(backgroundColor)
-        canvas.fillRect(0.0, 0.0, width, height)
+        canvas.setColor(theme.cardBackgroundColor)
+        canvas.fill()
 
         fun barGroupOffset(c: Int) = marginLeft + paddingLeft +
             (c) * barGroupWidth
@@ -97,13 +96,6 @@ class BarChart(
             canvas.fillCircle(x + barWidth - r, y + r, r)
             canvas.setFontSize(theme.smallTextSize)
             canvas.setTextAlign(TextAlign.CENTER)
-            canvas.setColor(backgroundColor)
-            canvas.fillRect(
-                x - barMargin,
-                y - theme.smallTextSize * 1.25,
-                barWidth + 2 * barMargin,
-                theme.smallTextSize * 1.0
-            )
             canvas.setColor(colors[s])
             canvas.drawText(
                 value.toShortString(),
@@ -119,12 +111,7 @@ class BarChart(
         fun drawMajorGrid() {
             canvas.setStrokeWidth(1.0)
             if (nSeries > 1) {
-                canvas.setColor(
-                    backgroundColor.blendWith(
-                        theme.lowContrastTextColor,
-                        0.5
-                    )
-                )
+                canvas.setColor(theme.lowContrastTextColor.withAlpha(0.5))
                 for (c in 0 until nColumns - 1) {
                     val x = barGroupOffset(c)
                     canvas.drawLine(x, paddingTop, x, paddingTop + maxBarHeight)
@@ -141,8 +128,6 @@ class BarChart(
 
         fun drawAxis() {
             val y = paddingTop + maxBarHeight
-            canvas.setColor(backgroundColor)
-            canvas.fillRect(0.0, y, width, height - y)
             canvas.setColor(theme.lowContrastTextColor)
             canvas.drawLine(0.0, y, width, y)
             canvas.setColor(theme.mediumContrastTextColor)
diff --git a/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/HistoryChart.kt b/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/HistoryChart.kt
index 193b7011c..4455bda28 100644
--- a/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/HistoryChart.kt
+++ b/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/HistoryChart.kt
@@ -33,7 +33,7 @@ class HistoryChart(
     var today: LocalDate,
     var paletteColor: PaletteColor,
     var theme: Theme,
-    var dateFormatter: LocalDateFormatter
+    var dateFormatter: LocalDateFormatter,
 ) : DataView {
 
     enum class Square {
@@ -61,8 +61,10 @@ class HistoryChart(
     override fun draw(canvas: Canvas) {
         val width = canvas.getWidth()
         val height = canvas.getHeight()
+
         canvas.setColor(theme.cardBackgroundColor)
-        canvas.fillRect(0.0, 0.0, width, height)
+        canvas.fill()
+
         squareSize = round((height - 2 * padding) / 8.0)
         canvas.setFontSize(height * 0.06)
 
@@ -98,7 +100,7 @@ class HistoryChart(
         canvas: Canvas,
         column: Int,
         topDate: LocalDate,
-        topOffset: Int
+        topOffset: Int,
     ) {
         drawHeader(canvas, column, topDate)
         repeat(7) { row ->
@@ -150,7 +152,7 @@ class HistoryChart(
         width: Double,
         height: Double,
         date: LocalDate,
-        offset: Int
+        offset: Int,
     ) {
 
         val value = if (offset >= series.size) Square.OFF else series[offset]
@@ -187,9 +189,13 @@ class HistoryChart(
             }
         }
 
-        val c1 = squareColor.contrast(theme.cardBackgroundColor)
-        val c2 = squareColor.contrast(theme.mediumContrastTextColor)
-        val textColor = if (c1 > c2) theme.cardBackgroundColor else theme.mediumContrastTextColor
+        val textColor = if (theme.cardBackgroundColor == Color.TRANSPARENT) {
+            theme.highContrastTextColor
+        } else {
+            val c1 = squareColor.contrast(theme.cardBackgroundColor)
+            val c2 = squareColor.contrast(theme.mediumContrastTextColor)
+            if (c1 > c2) theme.cardBackgroundColor else theme.mediumContrastTextColor
+        }
 
         canvas.setColor(textColor)
         canvas.setTextAlign(TextAlign.CENTER)
diff --git a/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/Themes.kt b/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/Themes.kt
index 525977858..5d46b9fcd 100644
--- a/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/Themes.kt
+++ b/android/uhabits-core/src/main/java/org/isoron/uhabits/core/ui/views/Themes.kt
@@ -66,9 +66,9 @@ abstract class Theme {
     val regularTextSize = 17.0
 }
 
-class LightTheme : Theme()
+open class LightTheme : Theme()
 
-class DarkTheme : Theme() {
+open class DarkTheme : Theme() {
     override val appBackgroundColor = Color(0x212121)
     override val cardBackgroundColor = Color(0x303030)
     override val headerBackgroundColor = Color(0x212121)
@@ -108,3 +108,10 @@ class DarkTheme : Theme() {
         }
     }
 }
+
+class WidgetTheme : LightTheme() {
+    override val cardBackgroundColor = Color.TRANSPARENT
+    override val highContrastTextColor = Color.WHITE
+    override val mediumContrastTextColor = Color.WHITE.withAlpha(0.50)
+    override val lowContrastTextColor = Color.WHITE.withAlpha(0.10)
+}
\ No newline at end of file
diff --git a/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/BarChartTest.kt b/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/BarChartTest.kt
index 97ac8a601..1b414b32a 100644
--- a/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/BarChartTest.kt
+++ b/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/BarChartTest.kt
@@ -46,6 +46,18 @@ class BarChartTest {
         assertRenders(300, 200, "$base/base.png", component)
     }
 
+    @Test
+    fun testDrawDarkTheme() = runBlocking {
+        component.theme = DarkTheme()
+        assertRenders(300, 200, "$base/themeDark.png", component)
+    }
+
+    @Test
+    fun testDrawWidgetTheme() = runBlocking {
+        component.theme = WidgetTheme()
+        assertRenders(300, 200, "$base/themeWidget.png", component)
+    }
+
     @Test
     fun testDrawWithOffset() = runBlocking {
         component.dataOffset = 5
diff --git a/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/HistoryChartTest.kt b/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/HistoryChartTest.kt
index 277659709..e9d8a8e87 100644
--- a/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/HistoryChartTest.kt
+++ b/android/uhabits-core/src/test/java/org/isoron/uhabits/core/ui/views/HistoryChartTest.kt
@@ -31,6 +31,7 @@ import org.isoron.uhabits.core.ui.views.HistoryChart.Square.HATCHED
 import org.isoron.uhabits.core.ui.views.HistoryChart.Square.OFF
 import org.isoron.uhabits.core.ui.views.HistoryChart.Square.ON
 import org.isoron.uhabits.core.ui.views.LightTheme
+import org.isoron.uhabits.core.ui.views.WidgetTheme
 import org.junit.Test
 import java.util.Locale
 
@@ -70,7 +71,6 @@ class HistoryChartTest {
     }
 
     // TODO: Label overflow
-    // TODO: Transparent
     // TODO: onClick
     // TODO: HistoryEditorDialog
     // TODO: Remove excessive padding on widgets
@@ -89,7 +89,13 @@ class HistoryChartTest {
     @Test
     fun testDrawDarkTheme() = runBlocking {
         view.theme = DarkTheme()
-        assertRenders(400, 200, "$base/dark.png", view)
+        assertRenders(400, 200, "$base/themeDark.png", view)
+    }
+
+    @Test
+    fun testDrawWidgetTheme() = runBlocking {
+        view.theme = WidgetTheme()
+        assertRenders(400, 200, "$base/themeWidget.png", view)
     }
 
     @Test