diff --git a/uhabits-android/build.gradle.kts b/uhabits-android/build.gradle.kts
index 8dc354c7f..022d7941e 100644
--- a/uhabits-android/build.gradle.kts
+++ b/uhabits-android/build.gradle.kts
@@ -37,7 +37,7 @@ android {
     defaultConfig {
         versionCode = 20100
         versionName = "2.1.0"
-        minSdk = 23
+        minSdk = 28
         targetSdk = 31
         applicationId = "org.isoron.uhabits"
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
diff --git a/uhabits-android/src/main/java/com/android/datetimepicker/Utils.java b/uhabits-android/src/main/java/com/android/datetimepicker/Utils.java
index 37dd730be..1a69f412b 100644
--- a/uhabits-android/src/main/java/com/android/datetimepicker/Utils.java
+++ b/uhabits-android/src/main/java/com/android/datetimepicker/Utils.java
@@ -22,7 +22,6 @@ import android.animation.Keyframe;
 import android.animation.ObjectAnimator;
 import android.animation.PropertyValuesHolder;
 import android.annotation.SuppressLint;
-import android.os.Build;
 import android.text.format.Time;
 import android.view.View;
 
@@ -43,17 +42,13 @@ public class Utils {
 
     static final String SHARED_PREFS_NAME = "com.android.calendar_preferences";
 
-    public static boolean isJellybeanOrLater() {
-      return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN;
-    }
-
     /**
      * Try to speak the specified text, for accessibility. Only available on JB or later.
      * @param text Text to announce.
      */
     @SuppressLint("NewApi")
     public static void tryAccessibilityAnnounce(View view, CharSequence text) {
-        if (isJellybeanOrLater() && view != null && text != null) {
+        if (view != null && text != null) {
             view.announceForAccessibility(text);
         }
     }
diff --git a/uhabits-android/src/main/java/com/android/datetimepicker/date/DayPickerView.java b/uhabits-android/src/main/java/com/android/datetimepicker/date/DayPickerView.java
index 05348fe8c..b18c358b0 100644
--- a/uhabits-android/src/main/java/com/android/datetimepicker/date/DayPickerView.java
+++ b/uhabits-android/src/main/java/com/android/datetimepicker/date/DayPickerView.java
@@ -383,10 +383,6 @@ public abstract class DayPickerView extends ListView implements OnScrollListener
             if (child instanceof MonthView) {
                 final CalendarDay focus = ((MonthView) child).getAccessibilityFocus();
                 if (focus != null) {
-                    if (Build.VERSION.SDK_INT == Build.VERSION_CODES.JELLY_BEAN_MR1) {
-                        // Clear focus to avoid ListView bug in Jelly Bean MR1.
-                        ((MonthView) child).clearAccessibilityFocus();
-                    }
                     return focus;
                 }
             }
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt b/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt
index f297b5e0d..28fbd63d8 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/activities/settings/SettingsFragment.kt
@@ -22,8 +22,6 @@ import android.app.backup.BackupManager
 import android.content.Intent
 import android.content.SharedPreferences
 import android.content.SharedPreferences.OnSharedPreferenceChangeListener
-import android.os.Build
-import android.os.Build.VERSION.SDK_INT
 import android.os.Bundle
 import android.provider.Settings
 import android.util.Log
@@ -98,7 +96,6 @@ class SettingsFragment : PreferenceFragmentCompat(), OnSharedPreferenceChangeLis
             showRingtonePicker()
             return true
         } else if (key == "reminderCustomize") {
-            if (SDK_INT < Build.VERSION_CODES.O) return true
             createAndroidNotificationChannel(requireContext())
             val intent = Intent(Settings.ACTION_CHANNEL_NOTIFICATION_SETTINGS)
             intent.putExtra(Settings.EXTRA_APP_PACKAGE, requireContext().packageName)
@@ -120,11 +117,7 @@ class SettingsFragment : PreferenceFragmentCompat(), OnSharedPreferenceChangeLis
         }
         updateWeekdayPreference()
 
-        if (SDK_INT < Build.VERSION_CODES.O)
-            findPreference("reminderCustomize").isVisible = false
-        else {
-            findPreference("reminderSound").isVisible = false
-        }
+        findPreference("reminderSound").isVisible = false
     }
 
     private fun updateWeekdayPreference() {
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt b/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt
index 47279f3d8..09d8f8b46 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/notifications/AndroidNotificationTray.kt
@@ -168,14 +168,12 @@ class AndroidNotificationTray
         fun createAndroidNotificationChannel(context: Context) {
             val notificationManager = context.getSystemService(Activity.NOTIFICATION_SERVICE)
                 as NotificationManager
-            if (SDK_INT >= Build.VERSION_CODES.O) {
-                val channel = NotificationChannel(
-                    REMINDERS_CHANNEL_ID,
-                    context.resources.getString(R.string.reminder),
-                    NotificationManager.IMPORTANCE_DEFAULT
-                )
-                notificationManager.createNotificationChannel(channel)
-            }
+            val channel = NotificationChannel(
+                REMINDERS_CHANNEL_ID,
+                context.resources.getString(R.string.reminder),
+                NotificationManager.IMPORTANCE_DEFAULT
+            )
+            notificationManager.createNotificationChannel(channel)
         }
     }
 }
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/utils/SystemUtils.kt b/uhabits-android/src/main/java/org/isoron/uhabits/utils/SystemUtils.kt
index 8fe759169..608abcff1 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/utils/SystemUtils.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/utils/SystemUtils.kt
@@ -21,18 +21,11 @@ package org.isoron.uhabits.utils
 import android.app.Activity
 import android.app.KeyguardManager
 import android.content.Context
-import android.os.Build
-import android.os.Build.VERSION.SDK_INT
-import android.view.WindowManager
 
 object SystemUtils {
 
     fun unlockScreen(activity: Activity) {
-        if (SDK_INT >= Build.VERSION_CODES.O) {
-            val km = activity.getSystemService(Context.KEYGUARD_SERVICE) as KeyguardManager
-            km.requestDismissKeyguard(activity, null)
-        } else {
-            activity.window.addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD)
-        }
+        val km = activity.getSystemService(Context.KEYGUARD_SERVICE) as KeyguardManager
+        km.requestDismissKeyguard(activity, null)
     }
 }
diff --git a/uhabits-android/src/main/java/org/isoron/uhabits/widgets/CheckmarkWidget.kt b/uhabits-android/src/main/java/org/isoron/uhabits/widgets/CheckmarkWidget.kt
index fbbb7ffd1..66d1da842 100644
--- a/uhabits-android/src/main/java/org/isoron/uhabits/widgets/CheckmarkWidget.kt
+++ b/uhabits-android/src/main/java/org/isoron/uhabits/widgets/CheckmarkWidget.kt
@@ -21,9 +21,7 @@ package org.isoron.uhabits.widgets
 
 import android.app.PendingIntent
 import android.content.Context
-import android.os.Build
 import android.view.View
-import androidx.annotation.RequiresApi
 import org.isoron.platform.gui.toInt
 import org.isoron.uhabits.core.models.Entry
 import org.isoron.uhabits.core.models.Habit
@@ -49,7 +47,6 @@ open class CheckmarkWidget(
         }
     }
 
-    @RequiresApi(Build.VERSION_CODES.O)
     override fun refreshData(widgetView: View) {
         (widgetView as CheckmarkWidgetView).apply {
             val today = DateUtils.getTodayWithOffset()
diff --git a/uhabits-android/src/main/res/drawable-v21/widget_button_background.xml b/uhabits-android/src/main/res/drawable-v21/widget_button_background.xml
deleted file mode 100644
index 9187c326a..000000000
--- a/uhabits-android/src/main/res/drawable-v21/widget_button_background.xml
+++ /dev/null
@@ -1,39 +0,0 @@
-<!--
-  ~ Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
-  ~
-  ~ This file is part of Loop Habit Tracker.
-  ~
-  ~ Loop Habit Tracker is free software: you can redistribute it and/or modify
-  ~ it under the terms of the GNU General Public License as published by the
-  ~ Free Software Foundation, either version 3 of the License, or (at your
-  ~ option) any later version.
-  ~
-  ~ Loop Habit Tracker is distributed in the hope that it will be useful, but
-  ~ WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-  ~ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
-  ~ more details.
-  ~
-  ~ You should have received a copy of the GNU General Public License along
-  ~ with this program. If not, see <http://www.gnu.org/licenses/>.
-  -->
-
-<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item
-        android:top="1dp"
-        android:left="1dp"
-        android:bottom="3dp"
-        android:right="3dp">
-        <ripple
-            android:color="#60ffffff">
-
-            <item android:id="@android:id/mask">
-                <shape android:shape="rectangle">
-                    <corners android:radius="5dp"/>
-                    <solid android:color="?android:colorPrimary"/>
-                </shape>
-                <color android:color="@color/white"/>
-            </item>
-        </ripple>
-    </item>
-
-</layer-list>
diff --git a/uhabits-android/src/main/res/drawable-v21/ripple.xml b/uhabits-android/src/main/res/drawable/ripple.xml
similarity index 100%
rename from uhabits-android/src/main/res/drawable-v21/ripple.xml
rename to uhabits-android/src/main/res/drawable/ripple.xml
diff --git a/uhabits-android/src/main/res/drawable-v21/ripple_transparent.xml b/uhabits-android/src/main/res/drawable/ripple_transparent.xml
similarity index 100%
rename from uhabits-android/src/main/res/drawable-v21/ripple_transparent.xml
rename to uhabits-android/src/main/res/drawable/ripple_transparent.xml
diff --git a/uhabits-android/src/main/res/drawable-v21/selected_box.xml b/uhabits-android/src/main/res/drawable/selected_box.xml
similarity index 100%
rename from uhabits-android/src/main/res/drawable-v21/selected_box.xml
rename to uhabits-android/src/main/res/drawable/selected_box.xml
diff --git a/uhabits-android/src/main/res/drawable/widget_button_background.xml b/uhabits-android/src/main/res/drawable/widget_button_background.xml
index 09785886f..9187c326a 100644
--- a/uhabits-android/src/main/res/drawable/widget_button_background.xml
+++ b/uhabits-android/src/main/res/drawable/widget_button_background.xml
@@ -17,18 +17,23 @@
   ~ with this program. If not, see <http://www.gnu.org/licenses/>.
   -->
 
-<selector xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:state_enabled="true" android:state_pressed="true">
-        <layer-list>
-            <item android:bottom="3dp"
-                  android:left="1dp"
-                  android:right="3dp"
-                  android:top="1dp">
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item
+        android:top="1dp"
+        android:left="1dp"
+        android:bottom="3dp"
+        android:right="3dp">
+        <ripple
+            android:color="#60ffffff">
+
+            <item android:id="@android:id/mask">
                 <shape android:shape="rectangle">
                     <corners android:radius="5dp"/>
-                    <solid android:color="#30ffffff"/>
+                    <solid android:color="?android:colorPrimary"/>
                 </shape>
+                <color android:color="@color/white"/>
             </item>
-        </layer-list>
+        </ripple>
     </item>
-</selector>
+
+</layer-list>
diff --git a/uhabits-android/src/main/res/mipmap-anydpi b/uhabits-android/src/main/res/mipmap-anydpi
new file mode 100644
index 000000000..e69de29bb
diff --git a/uhabits-android/src/main/res/values-v21/styles_list_habits.xml b/uhabits-android/src/main/res/values-v21/styles_list_habits.xml
deleted file mode 100644
index b433ddf8e..000000000
--- a/uhabits-android/src/main/res/values-v21/styles_list_habits.xml
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<!--
-  ~ Copyright (C) 2016-2021 Álinson Santos Xavier <git@axavier.org>
-  ~
-  ~ This file is part of Loop Habit Tracker.
-  ~
-  ~ Loop Habit Tracker is free software: you can redistribute it and/or modify
-  ~ it under the terms of the GNU General Public License as published by the
-  ~ Free Software Foundation, either version 3 of the License, or (at your
-  ~ option) any later version.
-  ~
-  ~ Loop Habit Tracker is distributed in the hope that it will be useful, but
-  ~ WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-  ~ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
-  ~ more details.
-  ~
-  ~ You should have received a copy of the GNU General Public License along
-  ~ with this program. If not, see <http://www.gnu.org/licenses/>.
-  -->
-
-<resources>
-
-</resources>
\ No newline at end of file