diff --git a/Makefile b/Makefile
index c6773a4e9a3373e3c45f870f2744bc25009f2ada..ff5be07e8f3586871fe705ee0c5506e603813caf 100644
--- a/Makefile
+++ b/Makefile
@@ -12,4 +12,8 @@ build-wasm:
 win-exe-icon:
 	windres -o main_rc_windows.syso main.rc
 
+arduino:
+	go run main.go build -target=arduino arduino.wa
+	wat2wasm a.out.wat -o a.out.wasm
+
 clean:
diff --git a/arduino.wa b/arduino.wa
new file mode 100644
index 0000000000000000000000000000000000000000..c2440ee76ec1685b52315138fd9dd79b22715501
--- /dev/null
+++ b/arduino.wa
@@ -0,0 +1,19 @@
+# 版权 @2022 凹语言 作者。保留所有权利。
+
+import "syscall/arduino"
+
+var LED = arduino.GetPinLED()
+
+fn init() {
+	arduino.PinMode(LED, 1)
+	arduino.Println("Wa is running 😎")
+}
+
+fn main() {
+	for {
+		arduino.DigitalWrite(LED, arduino.HIGH)
+		arduino.Delay(100)
+		arduino.DigitalWrite(LED, arduino.LOW)
+		arduino.Delay(900)
+	}
+}
diff --git a/internal/waroot/_waroot/src/runtime/runtime.wa b/internal/waroot/_waroot/src/runtime/runtime.wa
index dc074647f4db4429f0e0455c1f7d2f0e79163394..faaa0fa36a2fac380f5e4111fed725310dd1d44f 100644
--- a/internal/waroot/_waroot/src/runtime/runtime.wa
+++ b/internal/waroot/_waroot/src/runtime/runtime.wa
@@ -1,13 +1 @@
 # 版权 @2019 凹语言 作者。保留所有权利。
-
-#wa:import wa_js_env waPrintI32
-#wa:linkname $runtime.waPrintI32
-fn waPrintI32(i: i32)
-
-#wa:import wa_js_env waPrintRune
-#wa:linkname $runtime.waPrintRune
-fn waPrintRune(ch: i32)
-
-#wa:import wa_js_env waPuts
-#wa:linkname $runtime.waPuts
-fn waPuts(ptr: i32, len: i32)
diff --git a/internal/waroot/_waroot/src/runtime/runtime_arduino.wa b/internal/waroot/_waroot/src/runtime/runtime_arduino.wa
index f508959a071a3f512c6493003969b989c8f9f35a..8237592466bfa9112eeaaba2c1b3bcee391531c2 100644
--- a/internal/waroot/_waroot/src/runtime/runtime_arduino.wa
+++ b/internal/waroot/_waroot/src/runtime/runtime_arduino.wa
@@ -1,3 +1,12 @@
 # 版权 @2022 凹语言 作者。保留所有权利。
 
 var WAOS = "arduino"
+
+#wa:linkname $runtime.waPrintI32
+fn waPrintI32(i: i32) {}
+
+#wa:linkname $runtime.waPrintRune
+fn waPrintRune(ch: i32) {}
+
+#wa:linkname $runtime.waPuts
+fn waPuts(ptr: i32, len: i32) {}
diff --git a/internal/waroot/_waroot/src/runtime/runtime_chrome.wa b/internal/waroot/_waroot/src/runtime/runtime_chrome.wa
index d154102f2c08dfffa852c955f190a98c41267605..309402c8cb3f7c3aeb61f15f9f1785b55e3a96ef 100644
--- a/internal/waroot/_waroot/src/runtime/runtime_chrome.wa
+++ b/internal/waroot/_waroot/src/runtime/runtime_chrome.wa
@@ -1,3 +1,15 @@
 # 版权 @2022 凹语言 作者。保留所有权利。
 
 var WAOS = "chrome"
+
+#wa:import wa_js_env waPrintI32
+#wa:linkname $runtime.waPrintI32
+fn waPrintI32(i: i32)
+
+#wa:import wa_js_env waPrintRune
+#wa:linkname $runtime.waPrintRune
+fn waPrintRune(ch: i32)
+
+#wa:import wa_js_env waPuts
+#wa:linkname $runtime.waPuts
+fn waPuts(ptr: i32, len: i32)
diff --git a/internal/waroot/_waroot/src/runtime/runtime_walang.wa b/internal/waroot/_waroot/src/runtime/runtime_walang.wa
index 2da3aff2b8f7651f74d1ff95d89f1566b44a38dd..0a34fc6a021bb7c588be87a14be0b6daccf9622a 100644
--- a/internal/waroot/_waroot/src/runtime/runtime_walang.wa
+++ b/internal/waroot/_waroot/src/runtime/runtime_walang.wa
@@ -1,3 +1,15 @@
 # 版权 @2022 凹语言 作者。保留所有权利。
 
 var WAOS = "walang"
+
+#wa:import wa_js_env waPrintI32
+#wa:linkname $runtime.waPrintI32
+fn waPrintI32(i: i32)
+
+#wa:import wa_js_env waPrintRune
+#wa:linkname $runtime.waPrintRune
+fn waPrintRune(ch: i32)
+
+#wa:import wa_js_env waPuts
+#wa:linkname $runtime.waPuts
+fn waPuts(ptr: i32, len: i32)
diff --git a/internal/waroot/_waroot/src/runtime/runtime_wasi.wa b/internal/waroot/_waroot/src/runtime/runtime_wasi.wa
index 6008e424eaf2f53740297b19ea83daaa9047c33b..aab3268b323a00ab504dbb4fba046f6afda432a5 100644
--- a/internal/waroot/_waroot/src/runtime/runtime_wasi.wa
+++ b/internal/waroot/_waroot/src/runtime/runtime_wasi.wa
@@ -1,3 +1,15 @@
 # 版权 @2022 凹语言 作者。保留所有权利。
 
 var WAOS = "wasi"
+
+#wa:import wa_js_env waPrintI32
+#wa:linkname $runtime.waPrintI32
+fn waPrintI32(i: i32)
+
+#wa:import wa_js_env waPrintRune
+#wa:linkname $runtime.waPrintRune
+fn waPrintRune(ch: i32)
+
+#wa:import wa_js_env waPuts
+#wa:linkname $runtime.waPuts
+fn waPuts(ptr: i32, len: i32)
diff --git a/internal/waroot/_waroot/src/syscall/arduino/arduino.wa b/internal/waroot/_waroot/src/syscall/arduino/arduino.wa
index 63d0ee891dd7ec661ff465bea43f8c5711a7de3c..e53e160766cf653403ab868e65dfb2509951b7f7 100644
--- a/internal/waroot/_waroot/src/syscall/arduino/arduino.wa
+++ b/internal/waroot/_waroot/src/syscall/arduino/arduino.wa
@@ -1,33 +1,33 @@
 # 版权 @2022 凹语言 作者。保留所有权利。
 
-const (
-	LOW  = 0
-	HIGH = 1
+var (
+	LOW  :i32 = 0
+	HIGH :i32 = 1
 
-	INPUT        = 0
-	OUTPUT       = 1
-	INPUT_PULLUP = 2
+	INPUT        :i32 = 0
+	OUTPUT       :i32 = 1
+	INPUT_PULLUP :i32 = 2
 )
 
 #wa:import arduino millis
 #wa:linkname $waMillis
-fn Millis() => uint
+fn Millis() => i32
 
 #wa:import arduino delay
 #wa:linkname $waDelay
-fn Delay(ms: uint)
+fn Delay(ms: i32)
 
 #wa:import arduino pinMode
 #wa:linkname $waPinMode
-fn PinMode(pin, mode: uint)
+fn PinMode(pin, mode: i32)
 
 #wa:import arduino digitalWrite
 #wa:linkname $waDigitalWrite
-fn DigitalWrite(pin, value: uint)
+fn DigitalWrite(pin, value: i32)
 
 #wa:import arduino getPinLED
 #wa:linkname $waGetPinLED
-fn GetPinLED() => uint
+fn GetPinLED() => i32
 
 #wa:import arduino print
 #wa:linkname $waPrint
@@ -35,27 +35,13 @@ fn Print(s: string)
 
 #wa:import arduino getGreeting
 #wa:linkname $waGetGreeting
-fn _getGreeting(buf: *byte, maxlen: uint)
+fn _getGreeting(buf: *byte, maxlen: i32)
 
 fn Println(s: string) {
 	Print(s)
 	Print("\n")
 }
 
-fn GetGreeting() => string {
-	var buf = make([]byte, 64)
-	_getGreeting(&buf[0], 64)
-	# Find '\0'
-	n := -1
-	for i, b := range buf {
-		if b == 0 {
-			break
-		}
-		n = i
-	}
-	return string(buf[:n+1])
-}
-
 #wa:linkname $waPrintI32
 fn waPrintI32(i: i32) {
 	# TODO