diff --git a/src/Makefile b/src/Makefile
index b0c5f71..954b848 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2,7 +2,7 @@
 # -----------------------
 # Native build (gcc)
 CC_NATIVE = gcc
-CFLAGS_NATIVE = -g -std=c89 -Wall -Wextra -Werror -Wno-unused-parameter -I.
+CFLAGS_NATIVE = -g -O2 -std=c89 -Wall -Wextra -Werror -Wno-unused-parameter -I.
 LDFLAGS_NATIVE = 
 LDLIBS_NATIVE = -lSDL2
 
diff --git a/src/arch/linux/main.c b/src/arch/linux/main.c
index 5d935c7..6d270c6 100644
--- a/src/arch/linux/main.c
+++ b/src/arch/linux/main.c
@@ -13,8 +13,12 @@ int main(int argc, char **argv) {
   /* test_add_compile(&vm); */
   /* test_add_function_compile(&vm); */
   /* test_loop_compile(&vm); */
-  test_hello_world_compile(&vm);
-  /* test_recursive_function_compile(&vm); */
+  /* test_hello_world_compile(&vm); */
+  test_recursive_function_compile(&vm);
+
+  while(step_vm(&vm));
+
+  return 0;
 
   uint32_t buffer_size = 640 * 480 * sizeof(uint32_t);
 
@@ -58,6 +62,7 @@ int main(int argc, char **argv) {
   bool running = true;
   while (running) {
     step_vm(&vm);
+    SDL_PumpEvents();
     SDL_Event event;
     while (SDL_PollEvent(&event)) {
       switch (event.type) {
diff --git a/src/test.c b/src/test.c
index 0956563..e7b9a6e 100644
--- a/src/test.c
+++ b/src/test.c
@@ -34,6 +34,23 @@ bool test_add_compile(VM *vm) {
 }
 
 bool test_loop_compile(VM *vm) {
+  vm->memory[vm->mp++].u = 17;
+  vm->memory[vm->mp].c[0] = 'E';
+  vm->memory[vm->mp].c[1] = 'n';
+  vm->memory[vm->mp].c[2] = 't';
+  vm->memory[vm->mp++].c[3] = 'e';
+  vm->memory[vm->mp].c[0] = 'r';
+  vm->memory[vm->mp].c[1] = ' ';
+  vm->memory[vm->mp].c[2] = 'a';
+  vm->memory[vm->mp++].c[3] = ' ';
+  vm->memory[vm->mp].c[0] = 's';
+  vm->memory[vm->mp].c[1] = 't';
+  vm->memory[vm->mp].c[2] = 'r';
+  vm->memory[vm->mp++].c[3] = 'i';
+  vm->memory[vm->mp].c[0] = 'n';
+  vm->memory[vm->mp].c[1] = 'g';
+  vm->memory[vm->mp].c[2] = ':';
+  vm->memory[vm->mp++].c[3] = '\0';
   vm->code[vm->cp++].u = OP(OP_LOADF, 0, 0, 0); /* let a = 5.0 */
   vm->code[vm->cp++].f = 5.0f;
   vm->code[vm->cp++].u = OP(OP_LOADI, 1, 0, 0); /* do (i = 50000, 0, -1) { */
@@ -51,6 +68,9 @@ bool test_loop_compile(VM *vm) {
   vm->code[vm->cp++].u = OP(OP_ADD_INT, 1, 1, 3);  /* (implied by loop) i = i + (-1) */
   vm->code[vm->cp++].u = OP(OP_JGE_INT, 4, 1, 2);  /* } */
   vm->code[vm->cp++].u = OP(OP_REAL_TO_UINT, 1, 0, 0); /* let b = a as nat; */
+  vm->code[vm->cp++].u = OP(OP_LOADU, 5, 0, 0);
+  vm->code[vm->cp++].u = 0;
+  vm->code[vm->cp++].u = OP(OP_PRINT_STRING, 0, 5, 0); /* print("Enter a string: "); */
   vm->code[vm->cp++].u = OP(OP_READ_STRING, 2, 0, 0);  /* let user_string = gets(); */
   vm->code[vm->cp++].u = OP(OP_UINT_TO_STRING, 3, 1, 0);
   vm->code[vm->cp++].u = OP(OP_PRINT_STRING, 0, 3, 0); /* print(a.toS()); */
diff --git a/test/add.zl b/test/add.zl
new file mode 100644
index 0000000..8b90e5f
--- /dev/null
+++ b/test/add.zl
@@ -0,0 +1,5 @@
+fn add(a, b) {
+  return a + b;
+}
+let sum = add(1, 1);
+print sum;
diff --git a/test/add.zre b/test/add.zre
index 248e445..fd2bcea 100644
--- a/test/add.zre
+++ b/test/add.zre
@@ -1,6 +1,6 @@
-int add(int a, int b) {
+fn add(int a, int b) {
   return a + b;
 }
 
-int sum = add(1, 1);
+let sum = add(1, 1);
 print(sum.toS());
diff --git a/test/fib.zl b/test/fib.zl
new file mode 100644
index 0000000..1b95c65
--- /dev/null
+++ b/test/fib.zl
@@ -0,0 +1,7 @@
+fn fib(n) {
+  if (n < 2) return n;
+  return fib(n - 2) + fib(n - 1);
+}
+
+let result = fib(35);
+print result;
diff --git a/test/loop.asm b/test/loop.asm
index bfb52c0..1367b61 100644
--- a/test/loop.asm
+++ b/test/loop.asm
@@ -1,6 +1,10 @@
+.memory
+.ascii Enter a string:
+
+.code
 main:	
 	loadf $0 5.0
-	loadi $1 5
+	loadi $1 50000
 	loadi $2 0
 	loadi $3 -1
 loop:	
@@ -10,6 +14,8 @@ loop:
 	loadu $4 &loop
 	jgei $4 $1 $2
 	rtou $1 $0
+	loadu $5 0
+	puts $5
 	gets $2
 	utos $3 $1
 	puts $3
diff --git a/test/loop.lua b/test/loop.lua
index 2b5aa57..b1a8854 100644
--- a/test/loop.lua
+++ b/test/loop.lua
@@ -3,7 +3,7 @@ for i = 50000, 0, -1 do
   a = a + 5.0
 end
 local b = math.floor(a)
-io.write("Enter a string: ")
+io.write("Enter a string:")
 local user_string = io.read("*l")
 print(tostring(a))
 print(tostring(b))
diff --git a/test/loop.pl b/test/loop.pl
index 5183ae9..e2a2492 100644
--- a/test/loop.pl
+++ b/test/loop.pl
@@ -3,7 +3,7 @@ for (my $i = 50000; $i >= 0; $i--) {
   $a += 5.0;
 }
 my $b = int($a);
-print "Enter a string: ";
+print "Enter a string:";
 my $user_string = <STDIN>;
 chomp($user_string);
 print($a . "\n");
diff --git a/test/loop.py b/test/loop.py
index 16295c8..11cc9ba 100644
--- a/test/loop.py
+++ b/test/loop.py
@@ -2,7 +2,7 @@ a = 5.0
 for i in range(50000, -1, -1):
   a += 5.0
 b = int(a)
-user_string = input("Enter a string: ")
+user_string = input("Enter a string:")
 print(str(a))
 print(str(b))
 print(user_string)
diff --git a/test/loop.zl b/test/loop.zl
new file mode 100644
index 0000000..8ccc384
--- /dev/null
+++ b/test/loop.zl
@@ -0,0 +1,10 @@
+let a = 5.0;
+for (let i = 50000; i > 0; i = i - 1) {
+   a = a + 5.0;
+}
+let b = a;
+print "Enter a string:";
+let user_string = read();
+print(a);
+print(b);
+print(user_string);
diff --git a/test/run.sh b/test/run.sh
index 3be0756..de4ffdb 100755
--- a/test/run.sh
+++ b/test/run.sh
@@ -32,6 +32,10 @@ print_section "Perl ($FILENAME.pl)"
 print_section "Python ($FILENAME.py)"
  echo "test input" | time python3 "$FILENAME.py"
 
+# ZLC Implementation
+print_section "zlc ($FILENAME.zl)"
+ echo "test input" | time zlc "$FILENAME.zl"
+
 # ZRE Implementation
 print_section "zre ($FILENAME.zre)"
  echo "test input" | time ../src/zre "$FILENAME.zre"