diff --git a/CMakeLists.txt b/CMakeLists.txt
index d41ede5..7c3afb7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,3 +19,4 @@ add_subdirectory(code/vendors)
 
 add_subdirectory(code/apps/client)
 add_subdirectory(code/apps/server)
+add_subdirectory(code/apps/playground)
diff --git a/code/apps/playground/CMakeLists.txt b/code/apps/playground/CMakeLists.txt
new file mode 100644
index 0000000..102eb59
--- /dev/null
+++ b/code/apps/playground/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_executable(playground
+  source/main.c
+)
+
+include_directories(header)
+target_link_libraries(playground eco2d-common cwpack)
+link_system_libs(playground)
diff --git a/code/apps/playground/header/mock.h b/code/apps/playground/header/mock.h
new file mode 100644
index 0000000..0b4701c
--- /dev/null
+++ b/code/apps/playground/header/mock.h
@@ -0,0 +1,9 @@
+#pragma once
+
+uint64_t world_chunk_size(void) {
+    return 4;
+}
+
+uint64_t world_chunk_amount(void) {
+    return 8;
+}
diff --git a/code/apps/playground/source/main.c b/code/apps/playground/source/main.c
new file mode 100644
index 0000000..324efef
--- /dev/null
+++ b/code/apps/playground/source/main.c
@@ -0,0 +1,35 @@
+#define ZPL_IMPL
+#define ZPL_NANO
+#include <zpl.h>
+
+#include "mock.h"
+#include "packets/packet.h"
+
+int32_t mock_pkt_decode(pkt_desc *desc, uint32_t args, size_t msg_size, void *data, uint32_t size) {
+    pkt_header header = {
+        .data = pkt_buffer,
+        .datalen = msg_size
+    };
+    return pkt_msg_decode(&header, desc, args, data, size);
+}
+
+int main(void) {
+    pkt_01_welcome test_data = {
+        .chunk_size = world_chunk_size(),
+        .chunk_amount = world_chunk_amount()
+    };
+    
+    for (int i = 0; i < 4; i += 1){
+        test_data.numbers[i] = i*2;
+    }
+    
+    size_t msg_size = pkt_01_welcome_encode(&test_data);
+    pkt_01_welcome resp = {0};
+    if (mock_pkt_decode(pkt_01_welcome_desc, 3, msg_size, PKT_STRUCT_PTR(&resp))) {
+        zpl_printf("[err] oopsie!\n");
+    }
+    
+    zpl_printf("size %d, amt %d, num[1] %d struct %d msg %d\n", resp.chunk_size, resp.chunk_amount, resp.numbers[1], sizeof(pkt_01_welcome), msg_size);
+    
+    return 0;
+}
diff --git a/code/common/packets/packet.c b/code/common/packets/packet.c
index a283e73..d94cf2e 100644
--- a/code/common/packets/packet.c
+++ b/code/common/packets/packet.c
@@ -12,6 +12,7 @@ pkt_handler pkt_handlers[] = {
 };
 
 uint8_t pkt_buffer[PKT_BUFSIZ];
+uint8_t pkt_pack_buffer[PKT_BUFSIZ];
 
 int32_t pkt_header_encode(pkt_header *table) {
     return 0;
@@ -45,11 +46,15 @@ int32_t pkt_unpack_struct(cw_unpack_context *uc, pkt_desc *desc, void *raw_blob,
     for (pkt_desc *field = desc; field->type != CWP_NOT_AN_ITEM; ++field) {
         cw_unpack_next(uc);
         if (uc->item.type != field->type) return -1; // unexpected field
-        if (blob + field->offset + field->size >= blob + blob_size) return -1; // field does not fit
+        if (blob + field->offset + field->size > blob + blob_size) return -1; // field does not fit
         switch (field->type) {
             case CWP_ITEM_POSITIVE_INTEGER: {
                 zpl_memcopy(blob + field->offset, (uint8_t*)&uc->item.as.u64, field->size);
             }break;
+            case CWP_ITEM_BIN: {
+                if (uc->item.as.bin.length != field->size) return -1; // bin size mismatch
+                zpl_memcopy(blob + field->offset, (uint8_t*)uc->item.as.bin.start, uc->item.as.bin.length);
+            }break;
             default: {
                 zpl_printf("[WARN] unsupported pkt field type %lld !\n", field->type); 
                 return -1; // unsupported field
@@ -60,4 +65,25 @@ int32_t pkt_unpack_struct(cw_unpack_context *uc, pkt_desc *desc, void *raw_blob,
     return 0;
 }
 
-#include "packets/pkt_01_welcome.c"
\ No newline at end of file
+int32_t pkt_pack_struct(cw_pack_context *pc, pkt_desc *desc, void *raw_blob, uint32_t blob_size) {
+    uint8_t *blob = (uint8_t*)raw_blob;
+    zpl_zero_item(pkt_pack_buffer);
+    for (pkt_desc *field = desc; field->type != CWP_NOT_AN_ITEM; ++field) {
+        switch (field->type) {
+            case CWP_ITEM_BIN: {
+                cw_pack_bin(pc, blob + field->offset, field->size);
+            }break;
+            case CWP_ITEM_POSITIVE_INTEGER: {
+                uint64_t num;
+                zpl_memcopy(&num, blob + field->offset, field->size);
+                cw_pack_unsigned(pc, num);
+            }break;
+            default: {
+                zpl_printf("[WARN] unsupported pkt field type %lld !\n", field->type); 
+                return -1; // unsupported field
+            }break;
+        }
+    }
+    
+    return 0;
+}
diff --git a/code/common/packets/packet.h b/code/common/packets/packet.h
index c1a84f8..9288beb 100644
--- a/code/common/packets/packet.h
+++ b/code/common/packets/packet.h
@@ -29,5 +29,6 @@ int32_t pkt_header_decode(pkt_header *table, void *data, size_t datalen);
 
 extern pkt_handler pkt_handlers[];
 extern uint8_t pkt_buffer[];
+extern uint8_t pkt_pack_buffer[];
 
 #include "packet_list.h"
\ No newline at end of file
diff --git a/code/common/packets/packet_list.h b/code/common/packets/packet_list.h
index 8b7eabb..23b1b89 100644
--- a/code/common/packets/packet_list.h
+++ b/code/common/packets/packet_list.h
@@ -1,12 +1,20 @@
 #pragma once
+#include "packet_utils.h"
+#include "packet.h"
 
 // NOTE(zaklaus): pkt data
 
+#define PKT_01_NUMBERS_SIZ 32
+
 typedef struct {
     uint32_t chunk_size;
     uint32_t chunk_amount;
+    uint16_t numbers[PKT_01_NUMBERS_SIZ];
 } pkt_01_welcome;
 
+size_t pkt_01_welcome_encode(pkt_01_welcome *table);
+extern pkt_desc pkt_01_welcome_desc[];
+
 // NOTE(zaklaus): pkt handlers
 
 PKT_HANDLER_PROC(pkt_01_welcome_handler);
diff --git a/code/common/packets/packet_utils.h b/code/common/packets/packet_utils.h
index 1ad62ed..b8ece1d 100644
--- a/code/common/packets/packet_utils.h
+++ b/code/common/packets/packet_utils.h
@@ -49,7 +49,11 @@ inline size_t pkt_pack_msg_size(cw_pack_context *pc) {
 #endif
 
 #ifndef PKT_FIELD
-#define PKT_FIELD(k, t, a) .type = k, .offset = PKT_OFFSETOF(t, a), .size = PKT_FIELD_SIZEOF(t,a)
+#define PKT_FIELD(k, t, a) .type = k, .offset = PKT_OFFSETOF(t, a), .size = PKT_FIELD_SIZEOF(t,a), .it_size = PKT_FIELD_SIZEOF(t,a)
+#endif
+
+#ifndef PKT_ARRAY
+#define PKT_ARRAY(t, a) .type = CWP_ITEM_BIN, .offset = PKT_OFFSETOF(t, a), .size = PKT_FIELD_SIZEOF(t,a), .it_size = PKT_FIELD_SIZEOF(t,a[0])
 #endif
 
 #ifndef PKT_END
@@ -64,14 +68,15 @@ typedef struct pkt_desc {
     cwpack_item_types type;
     size_t offset;
     size_t size;
+    size_t it_size;
 } pkt_desc;
     
 int32_t pkt_unpack_struct(cw_unpack_context *uc, pkt_desc *desc, void *raw_blob, uint32_t blob_size);
 
 inline int32_t pkt_msg_decode(pkt_header *header, pkt_desc* desc, uint32_t args, void *raw_blob, uint32_t blob_size) {
     cw_unpack_context uc = {0};
-    pkt_unpack_msg(&uc, header, args);
-    pkt_unpack_struct(&uc, desc, header, raw_blob, blob_size);
+    PKT_IF(pkt_unpack_msg(&uc, header, args));
+    PKT_IF(pkt_unpack_struct(&uc, desc, raw_blob, blob_size));
     
     return pkt_validate_eof_msg(&uc);
 }
\ No newline at end of file
diff --git a/code/common/packets/pkt_01_welcome.c b/code/common/packets/pkt_01_welcome.c
index e183b08..da651f4 100644
--- a/code/common/packets/pkt_01_welcome.c
+++ b/code/common/packets/pkt_01_welcome.c
@@ -1,28 +1,24 @@
 #include "packet.h"
 #include "packet_utils.h"
 
-#ifdef SERVER
-size_t pkt_01_welcome_encode(pkt_01_welcome *table) {
-    cw_pack_context pc = {0};
-    pkt_pack_msg(&pc, PKT_01_WELCOME_ARGS);
-
-    cw_pack_unsigned(&pc, world_chunk_size());
-    cw_pack_unsigned(&pc, world_chunk_amount());
-
-    return pkt_pack_msg_size(&pc);
-}
-#else
-pkt_desc pkt_01_welcome_desc[3] = {
+pkt_desc pkt_01_welcome_desc[] = {
     { PKT_FIELD(CWP_ITEM_POSITIVE_INTEGER, pkt_01_welcome, chunk_size) },
     { PKT_FIELD(CWP_ITEM_POSITIVE_INTEGER, pkt_01_welcome, chunk_amount) },
+    { PKT_ARRAY(pkt_01_welcome, numbers) },
     { PKT_END },
 };
 
+size_t pkt_01_welcome_encode(pkt_01_welcome *table) {
+    cw_pack_context pc = {0};
+    pkt_pack_msg(&pc, 3);
+    pkt_pack_struct(&pc, pkt_01_welcome_desc, PKT_STRUCT_PTR(table));
+    return pkt_pack_msg_size(&pc);
+}
+
 int32_t pkt_01_welcome_handler(pkt_header *header) {
     pkt_01_welcome table;
-    PKT_IF(pkt_msg_decode(header, pkt_01_welcome_desc, 2, PKT_STRUCT_PTR(&table)));
+    PKT_IF(pkt_msg_decode(header, pkt_01_welcome_desc, 3, PKT_STRUCT_PTR(&table)));
 
     zpl_printf("we received: chunk_size: %d and chunk_amount: %d\n", table.chunk_size, table.chunk_amount);
     return 0;
 }
-#endif
\ No newline at end of file
diff --git a/code/common/packets/pkt_01_welcome.h b/code/common/packets/pkt_01_welcome.h
new file mode 100644
index 0000000..3f59c93
--- /dev/null
+++ b/code/common/packets/pkt_01_welcome.h
@@ -0,0 +1,2 @@
+#pragma once
+