diff --git a/examples/first/first.c b/examples/first/first.c
index 9603d54..9e6b247 100644
--- a/examples/first/first.c
+++ b/examples/first/first.c
@@ -4,13 +4,15 @@ int main(void)
 {
   uint8_t value = 0;
 
+  card_os_put_rect((card_os_rect){ 0, 0, 0, 0, 0, 240, 320 });
+
+  card_os_put_rect((card_os_rect){
+    .r = 0xFF, .g = 0xFF, .b = 0xFF, .x = 60, .y = 80, .w = 120, .h = 160 });
+
   while (value < 250)
   {
-
     card_os_put_rect((card_os_rect){
-      .r = value++, .g = 0, .b = 0, .x = 0, .y = 0, .w = 240, .h = 320 });
-    card_os_put_rect((card_os_rect){
-      .r = 0xFF, .g = 0xFF, .b = 0xFF, .x = 60, .y = 80, .w = 60, .h = 60 });
+      .r = value++, .g = 0, .b = 0, .x = 0, .y = 0, .w = 60, .h = 60 });
   }
 
   return 0;
diff --git a/include/user/card-os.h b/include/user/card-os.h
index 56bda63..267fcb7 100644
--- a/include/user/card-os.h
+++ b/include/user/card-os.h
@@ -5,7 +5,6 @@
 
 typedef enum
 {
-  OS_CMD_TERMINATE_PROGRAM,
   OS_CMD_SBRK,
   OS_CMD_DRAW_RECT
 } os_command;
diff --git a/src/card-os-user.c b/src/card-os-user.c
index 046b34d..d2b95a7 100644
--- a/src/card-os-user.c
+++ b/src/card-os-user.c
@@ -13,13 +13,7 @@ ssize_t _read(int file, void* ptr, size_t len) { return 0; }
 
 ssize_t _write(int file, const void* ptr, size_t len) { return len; }
 
-void _exit(int status)
-{
-  oscall(&(os_message){ .command = OS_CMD_TERMINATE_PROGRAM, .data = NULL });
-  while (1)
-  {
-  }
-}
+void _exit(int status) {}
 
 void* _sbrk(ptrdiff_t incr)
 {
@@ -37,12 +31,12 @@ extern uint8_t __bss_start__;
 extern uint8_t __bss_end__;
 int main(void);
 
-__attribute__((section(".start"))) void _start(void)
+__attribute__((section(".start"))) int _start(void)
 {
   for (uint8_t* p = &__bss_start__; p < &__bss_end__; p++)
   {
     *p = 0;
   }
 
-  _exit(main());
+  return main();
 }
diff --git a/src/card-os.c b/src/card-os.c
index cca2ca8..309c372 100644
--- a/src/card-os.c
+++ b/src/card-os.c
@@ -89,14 +89,15 @@ void tud_vendor_rx_cb(uint8_t itf, const uint8_t* buffer, uint16_t bufsize)
       case RECV_LOW8_LENGTH:
         program_length |= buffer[bufidx];
         recv_status = RECV_PROGRAM;
+        memset(&__user_ram_start, 0, 0x10000);
         break;
 
       case RECV_PROGRAM:
         (&__user_ram_start)[program_write_index++] = buffer[bufidx];
         if (program_write_index == program_length)
         {
-          __dmb();
           user_program = (user_program_fn)((uintptr_t)&__user_ram_start | 1);
+          __dmb();
           __sev();
           recv_status = RECV_WAITING;
         }
@@ -113,25 +114,19 @@ static volatile os_ring_buffer core1_buffer
 
 void core1_entry(void)
 {
-  while (!user_program)
-  {
-    __wfe();
-  }
-
-  user_program();
-
-  // send message to terminate core 1
-  int index = -1;
-  while (index < 0)
-  {
-    index = os_ring_buffer_write(&core1_buffer,
-                                 &(os_message){ .command = 1, .data = NULL });
-  }
-  multicore_fifo_push_blocking(index);
-
-  // stall until reset
   while (true)
   {
+    while (!user_program)
+    {
+      __wfe();
+    }
+
+    user_program_fn copied = user_program;
+    user_program = NULL;
+    __dmb();
+    __sev();
+
+    int retrval = copied();
   }
 }
 
@@ -191,14 +186,6 @@ void os_handle_message(const os_message* msg, os_message* out)
 {
   switch (msg->command)
   {
-  case OS_CMD_TERMINATE_PROGRAM:
-    multicore_fifo_drain();
-    multicore_reset_core1();
-    __dmb();
-    user_program = NULL;
-    __sev();
-    multicore_launch_core1(core1_entry);
-    break;
   case OS_CMD_SBRK:
     os_sbrk(msg->data, &out->data);
     break;