diff --git a/bin/android-builder b/bin/android-builder
index 8321ce8..549af11 100755
--- a/bin/android-builder
+++ b/bin/android-builder
@@ -2,23 +2,199 @@
 set -e
 
 AB_HOME="${ANDROID_BUILDER_HOME:-$HOME/android-builder}"
+SDK="$HOME/android-sdk"
+PLATFORM="${ANDROID_BUILDER_PLATFORM:-android-33}"
+
+install_packages() {
+  echo "==> Installing Termux packages"
+  pkg update -y
+  pkg install -y git curl wget unzip zip nano \
+    openjdk-21 gradle aapt2 apksigner d8 dx android-tools
+}
+
+configure_java() {
+  echo "==> Configuring Java"
+
+  JAVA_BIN="$(command -v java || true)"
+
+  if [ -z "$JAVA_BIN" ]; then
+    echo "ERROR: java not found after installing openjdk-21."
+    exit 1
+  fi
+
+  JAVA_HOME_DETECTED="$(dirname "$(dirname "$(readlink -f "$JAVA_BIN")")")"
+
+  export JAVA_HOME="$JAVA_HOME_DETECTED"
+  export PATH="$JAVA_HOME/bin:$PATH"
+
+  touch "$HOME/.bashrc"
+
+  grep -q 'ANDROID_BUILDER_JAVA_HOME' "$HOME/.bashrc" || cat >> "$HOME/.bashrc" <<EOF
+
+# Java for AndroidBuilder
+export JAVA_HOME=$JAVA_HOME_DETECTED
+export PATH=\$JAVA_HOME/bin:\$PATH
+export ANDROID_BUILDER_JAVA_HOME=\$JAVA_HOME
+EOF
+
+  java -version
+  echo "JAVA_HOME=$JAVA_HOME"
+}
+
+install_cmdline_tools() {
+  echo "==> Installing Android SDK cmdline-tools"
+
+  mkdir -p "$SDK/cmdline-tools"
+  cd "$SDK/cmdline-tools"
+
+  if [ ! -d latest ]; then
+    wget https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip -O cmdline-tools.zip
+    unzip -q cmdline-tools.zip
+    mv cmdline-tools latest
+    rm cmdline-tools.zip
+  fi
+}
+
+configure_android_environment() {
+  echo "==> Configuring Android SDK environment"
+
+  touch "$HOME/.bashrc"
+
+  grep -q 'ANDROID_HOME' "$HOME/.bashrc" || cat >> "$HOME/.bashrc" <<'EOF'
+
+# AndroidBuilder SDK environment
+export ANDROID_HOME=$HOME/android-sdk
+export ANDROID_SDK_ROOT=$ANDROID_HOME
+export PATH=$ANDROID_HOME/cmdline-tools/latest/bin:$PATH
+EOF
+
+  export ANDROID_HOME="$SDK"
+  export ANDROID_SDK_ROOT="$SDK"
+  export PATH="$SDK/cmdline-tools/latest/bin:$PATH"
+}
+
+accept_licenses() {
+  echo "==> Accepting Android SDK licenses"
+
+  mkdir -p "$SDK/licenses"
+
+  cat > "$SDK/licenses/android-sdk-license" <<'EOF'
+24333f8a63b6825ea9c5514f83c2829b004d1fee
+d56f5187479451eabf01fb78af6dfcb131a6481e
+8933bad161af4178b1185d1a37fbf41ea5269c55
+EOF
+}
+
+install_sdk_platform() {
+  echo "==> Installing SDK platform: $PLATFORM"
+
+  command -v java >/dev/null || {
+    echo "ERROR: Java is not available."
+    exit 1
+  }
+
+  command -v sdkmanager >/dev/null || {
+    echo "ERROR: sdkmanager not found."
+    exit 1
+  }
+
+  sdkmanager "platforms;$PLATFORM"
+}
+
+configure_gradle() {
+  echo "==> Writing Gradle config"
+
+  mkdir -p "$HOME/.gradle"
+
+  cat > "$HOME/.gradle/gradle.properties" <<EOF
+org.gradle.jvmargs=-Xmx4096m -Dfile.encoding=UTF-8
+org.gradle.daemon=true
+org.gradle.parallel=true
+org.gradle.caching=true
+android.aapt2FromMavenOverride=$PREFIX/bin/aapt2
+EOF
+}
+
+setup() {
+  install_packages
+  configure_java
+  install_cmdline_tools
+  configure_android_environment
+  accept_licenses
+  install_sdk_platform
+  configure_gradle
+
+  echo
+  echo "Setup complete."
+  echo "Run:"
+  echo "  source ~/.bashrc"
+  echo "  android-builder doctor"
+}
+
+doctor() {
+  echo "AndroidBuilder Doctor"
+  echo
+
+  echo "Java:"
+  java -version || true
+  echo
+
+  echo "Gradle:"
+  gradle -v | grep Gradle || true
+  echo
+
+  echo "AAPT2:"
+  aapt2 version || true
+  echo
+
+  echo "SDK:"
+  echo "$SDK"
+  test -f "$SDK/platforms/$PLATFORM/android.jar" \
+    && echo "android.jar: found" \
+    || echo "android.jar: missing"
+}
+
+build() {
+  test -f local.properties || echo "sdk.dir=$SDK" > local.properties
+
+  if [ -f ./gradlew ]; then
+    chmod +x ./gradlew
+    ./gradlew assembleDebug
+  else
+    gradle assembleDebug
+  fi
+}
+
+install_apk() {
+  APK=$(find . -path "*/build/outputs/apk/debug/*.apk" -type f | head -n 1)
+
+  if [ -z "$APK" ]; then
+    echo "No debug APK found."
+    exit 1
+  fi
+
+  termux-open "$APK"
+}
+
+help() {
+  echo "AndroidBuilder"
+  echo
+  echo "Usage:"
+  echo "  android-builder setup"
+  echo "  android-builder doctor"
+  echo "  android-builder build"
+  echo "  android-builder install"
+}
+
 COMMAND="$1"
 shift || true
 
 case "$COMMAND" in
-  setup)
-    echo "Setup command not implemented yet."
-    ;;
-  doctor)
-    echo "Doctor command not implemented yet."
-    ;;
-  help|-h|--help|"")
-    echo "AndroidBuilder"
-    echo
-    echo "Usage:"
-    echo "  android-builder setup"
-    echo "  android-builder doctor"
-    ;;
+  setup) setup "$@" ;;
+  doctor) doctor "$@" ;;
+  build) build "$@" ;;
+  install) install_apk "$@" ;;
+  help|-h|--help|"") help ;;
   *)
     echo "Unknown command: $COMMAND"
     echo "Run: android-builder help"