diff --git a/build_file.c b/build_file.c
index 30b85c7..0f53b5e 100644
--- a/build_file.c
+++ b/build_file.c
@@ -41,7 +41,7 @@ int main(int argc, char **argv) {
         ok = os_systemf(
             "cl ../src/core_test/core_test_entry.c -Fe:core_test.exe -Fd:core_test.pdb"
             " -I ../src"
-            " /Zi /FC /nologo /Oi"
+            " /Zi /FC /nologo /Oi /O2"
             " /WX /W3 /wd4200 /diagnostics:column"
             " /link /incremental:no"
         );
diff --git a/package/index.html b/package/index.html
index b324d59..daa7a63 100644
--- a/package/index.html
+++ b/package/index.html
@@ -104,6 +104,9 @@ const mem = new memory_t(new WebAssembly['Memory']({ initial: 2000, maximum: 655
             ctx2d.fillStyle = `rgba(${r}, ${g}, ${b}, ${a})`;
             ctx2d.fill();
         },
+        wasm_clear: () => {
+            ctx2d.clearRect(0, 0, canvas.width, canvas.height);
+        },
         wasm_set_clip: (x, y, w, h) => {
             ctx2d.restore();
             ctx2d.save();
@@ -115,6 +118,11 @@ const mem = new memory_t(new WebAssembly['Memory']({ initial: 2000, maximum: 655
             return parseFloat(mem.read_cstr(str, len));
         },
         wasm_trap: () => { throw new Error() },
+        wasm_alert: (str, len) => {
+            const string = mem.read_cstr(str,len);
+            console.log(string);
+            alert(string);
+        },
     };
 
     const program = await WebAssembly['instantiate'](binary, { "env": wasm_imports });
diff --git a/src/app/app_wasm.c b/src/app/app_wasm.c
index 944f992..c24b951 100644
--- a/src/app/app_wasm.c
+++ b/src/app/app_wasm.c
@@ -2,8 +2,11 @@
 #define fn_wasm_export __attribute__((visibility("default")))
 #define fn_wasm_import
 
+fn_wasm_import void wasm_alert(isize ptr, i32 len);
 fn_wasm_import f64  wasm_parse_float(isize str, i32 len);
 fn_wasm_import void wasm_write_to_console(isize str, i32 len);
+
+fn_wasm_import void wasm_clear();
 fn_wasm_import void wasm_draw_text(isize str, i32 len, f64 x, f64 y, isize font_str, i32 font_len, i32 font_size, f32 r, f32 g, f32 b, f32 a);
 fn_wasm_import void wasm_draw_rect(f64 x, f64 y, f64 w, f64 h, f32 r, f32 g, f32 b, f32 a);
 fn_wasm_import f64  wasm_measure_text(isize str, i32 len, isize font_str, i32 font_len, i32 font_size);
@@ -27,13 +30,16 @@ glb    f64                    wasm_last_time = 0;
 
 fn void app_update(ma_arena_t *perm_arena, app_event_t *events, i32 event_count);
 
+fn void alert(s8_t string) {
+    wasm_alert((isize)string.str, (i32)string.len);
+}
 
 fn void puts(const char *string) {
     wasm_write_to_console((isize)string, (i32)str_len((char *)string));
 }
 
 fn double strtod(const char *str, char **end_unused) {
-    assertf(end_unused == NULL, "second parameter should be null!!");
+    assert(end_unused == NULL);
     return wasm_parse_float((isize)str, str_len((char *)str));
 }
 
@@ -183,14 +189,17 @@ fn_wasm_export void wasm_key_up(char *key, b32 ctrl, b32 shift, b32 alt, b32 met
 
 fn_wasm_export void wasm_update(f64 time, f64 width, f64 height, f64 dpr) {
     f64 delta_time = (time - wasm_last_time);
+    v2f32_t window_size = (v2f32_t){width / dpr, height / dpr};
     for (i32 i = 0; i < wasm_events.len; i += 1) {
         wasm_events.data[i].dpr = dpr;
-        wasm_events.data[i].window_size = (v2f32_t){width / dpr, height / dpr};
+        wasm_events.data[i].window_size = window_size;
         wasm_events.data[i].time = time;
         wasm_events.data[i].delta_time = delta_time;
     }
     wasm_dpr = dpr;
 
+    wasm_clear();
+    draw_rect(r2f64(0, 0, window_size.x, window_size.y), white_color_global);
     app_update(&wasm_perm_arena, wasm_events.data, wasm_events.len);
 
     wasm_events.len = 0;
@@ -199,12 +208,24 @@ fn_wasm_export void wasm_update(f64 time, f64 width, f64 height, f64 dpr) {
 }
 
 fn_wasm_export void wasm_init(void) {
-    isize page_size = kib(64);
-    isize page_count = __builtin_wasm_memory_size(0);
-    u8 *memory = (u8 *)&__heap_base;
-    usize memory_size = page_count * (page_size) - (isize)memory;
-    wasm_perm_arena.data = memory;
-    wasm_perm_arena.commit = wasm_perm_arena.reserve = memory_size;
+    {
+        isize page_size = kib(64);
+        isize page_count = __builtin_wasm_memory_size(0);
+        u8 *memory = (u8 *)&__heap_base;
+        usize memory_size = page_count * (page_size) - (isize)memory;
+        wasm_perm_arena.data = memory;
+        wasm_perm_arena.commit = wasm_perm_arena.reserve = memory_size;
+
+        // init core
+        {
+            ma_push_arena_ex(&wasm_perm_arena, &core_desc.scratch[0], mib(1));
+            ma_push_arena_ex(&wasm_perm_arena, &core_desc.scratch[1], kib(256));
+            ma_push_arena_ex(&wasm_perm_arena, &core_desc.scratch[2], kib(64));
+        }
+
+        debugf("on_init, __builtin_wasm_memory_size(0) = %d(%d)", page_count, memory_size);
+    }
+
     wasm_input_text_arena = ma_push_arena(&wasm_perm_arena, kib(1));
-    debugf("on_init, __builtin_wasm_memory_size(0) = %d(%d)", page_count, memory_size);
+
 }
\ No newline at end of file
diff --git a/src/core/core.c b/src/core/core.c
index 6283de3..c742fec 100644
--- a/src/core/core.c
+++ b/src/core/core.c
@@ -18,8 +18,9 @@
 #endif
 
 #if PLATFORM_WASM
-double strtod(const char *str, char **end_unused);
-void puts(const char *str);
+fn double strtod(const char *str, char **end_unused);
+fn void puts(const char *str);
+fn void alert(s8_t string);
 #endif
 
 #if PLATFORM_CL
diff --git a/src/core/core_arena.c b/src/core/core_arena.c
index cebd62e..a230244 100644
--- a/src/core/core_arena.c
+++ b/src/core/core_arena.c
@@ -83,6 +83,7 @@ fn void *ma_push_size_ex(ma_arena_t *arena, usize size) {
             }
         }
         if (new_len > arena->commit) {
+            invalid_codepath;
             return NULL;
         }
     }
@@ -98,12 +99,16 @@ fn void *ma_push_size(ma_arena_t *arena, usize size) {
     return result;
 }
 
-fn ma_arena_t *ma_push_arena(ma_arena_t *allocator, usize size) {
-    ma_arena_t *result   = ma_push_type(allocator, ma_arena_t);
+fn void ma_push_arena_ex(ma_arena_t *allocator, ma_arena_t *result, usize size) {
     result->data    = (u8 *)ma_push_size(allocator, size);
     result->reserve = size;
     result->commit  = size;
     result->align   = ma_default_alignment;
+}
+
+fn ma_arena_t *ma_push_arena(ma_arena_t *allocator, usize size) {
+    ma_arena_t *result   = ma_push_type(allocator, ma_arena_t);
+    ma_push_arena_ex(allocator, result, size);
     return result;
 }
 
@@ -151,7 +156,7 @@ fn ma_temp_t ma_begin_scratch_ex(ma_arena_t **conflicts, int conflict_count) {
         }
     }
 
-    assertf(unoccupied, "Failed to get free scratch memory, this is a fatal error, this shouldnt happen");
+    assert(unoccupied); // failed to get free scratch memory, this is a fatal error, this shouldnt happen
     ma_temp_t result = ma_begin_temp(unoccupied);
     return result;
 }
diff --git a/src/core/core_arena.h b/src/core/core_arena.h
index bdd2227..f60faeb 100644
--- a/src/core/core_arena.h
+++ b/src/core/core_arena.h
@@ -26,9 +26,10 @@ fn void        ma_destroy(ma_arena_t *arena);
 
 //
 // push
-fn void       *ma_push_size_ex(ma_arena_t *arena, usize size);
 fn void       *ma_push_size(ma_arena_t *arena, usize size);
+fn void       *ma_push_size_ex(ma_arena_t *arena, usize size);
 fn ma_arena_t *ma_push_arena(ma_arena_t *allocator, usize size);
+fn void        ma_push_arena_ex(ma_arena_t *allocator, ma_arena_t *result, usize size);
 #define ma_push_type(arena, Type) (Type *)ma_push_size((arena), sizeof(Type))
 #define ma_push_array(arena, Type, count) (Type *)ma_push_size((arena), sizeof(Type) * (count))
 
diff --git a/src/core/core_defines.h b/src/core/core_defines.h
index 05db35e..82ef22f 100644
--- a/src/core/core_defines.h
+++ b/src/core/core_defines.h
@@ -46,6 +46,7 @@ typedef double f64;
 #ifndef offsetof
 #define offsetof(st, m) ((usize)&(((st *)0)->m))
 #endif
+#define expect(x) if (!(x))
 
 #define kib(x) (1024ULL * (x##ULL))
 #define mib(x) (1024ULL * kib(x))
diff --git a/src/core/core_intrin.c b/src/core/core_intrin.c
index c554f98..c59cbdf 100644
--- a/src/core/core_intrin.c
+++ b/src/core/core_intrin.c
@@ -87,16 +87,6 @@ fn f64 f64_from_s8(s8_t string) {
     return result;
 }
 
-fn void core_print_message(s8_t string) {
-    ma_temp_t scratch = ma_begin_scratch();
-    s8_t copy = s8_printf(scratch.arena, "%S\n", string);
-#if PLATFORM_WINDOWS
-    OutputDebugStringA(copy.str);
-#endif
-    puts(copy.str);
-    ma_end_scratch(scratch);
-}
-
 fn date_t date_now(void) {
     date_t result = {0};
 #if PLATFORM_WASM
@@ -121,4 +111,4 @@ fn date_t date_now(void) {
     result.year = lt->tm_year;
 #endif
     return result;
-}
\ No newline at end of file
+}
diff --git a/src/core/core_intrin.h b/src/core/core_intrin.h
index 6fcb752..f6be258 100644
--- a/src/core/core_intrin.h
+++ b/src/core/core_intrin.h
@@ -35,6 +35,6 @@ THREAD_LOCAL core_desc_t core_desc = {
     .log = {
         .break_on_fatal = true,
         .log_proc = default_log_proc,
-        .flags = log_flag_all,
+        .flags = 0,
     }
 };
diff --git a/src/core/core_log.c b/src/core/core_log.c
index 8e6dbd8..9590f99 100644
--- a/src/core/core_log.c
+++ b/src/core/core_log.c
@@ -1,11 +1,11 @@
-fn s8_t log_level_str(log_level_t level) {
+fn char *log_level_str(log_level_t level) {
     switch(level) {
-    case log_level_debug: return s8_lit("DEBUG");
-    case log_level_info: return s8_lit("INFO");
-    case log_level_warning: return s8_lit("WARN");
-    case log_level_error: return s8_lit("ERROR");
-    case log_level_fatal: return s8_lit("FATAL");
-    default: return s8_lit("INVALID");
+    case log_level_debug: return "DEBUG";
+    case log_level_info: return "INFO";
+    case log_level_warning: return "WARN";
+    case log_level_error: return "ERROR";
+    case log_level_fatal: return "FATAL";
+    default: return "INVALID";
     }
 }
 
@@ -20,6 +20,17 @@ fn void log_basef(i32 module, log_level_t level, s8_t file_and_line, const char
     ma_end_scratch(scratch);
 }
 
+fn void core_error_message(char *str) {
+#if PLATFORM_WINDOWS
+    MessageBoxA(NULL, str, "fatal error", MB_OK);
+    fprintf(stderr, "%s", str);
+#elif PLATFORM_WASM
+    alert(s8_from_char(str));
+#else
+    fprintf(stderr, "%s", str);
+#endif
+}
+
 fn void default_log_proc(log_event_t ev) {
     ma_temp_t scratch = ma_begin_scratch();
     sb8_t *sb = sb8_serial_begin(scratch.arena);
@@ -27,7 +38,7 @@ fn void default_log_proc(log_event_t ev) {
         sb8_printf(sb, "[%d] ", ev.module);
     }
     if (core_desc.log.flags & log_flag_level) {
-        sb8_printf(sb, "%-5S ", log_level_str(ev.level));
+        sb8_printf(sb, "%-5s ", log_level_str(ev.level));
     }
     date_t date = {0};
     {
@@ -47,23 +58,25 @@ fn void default_log_proc(log_event_t ev) {
         sb8_printf(sb, "%-40S ", ev.file_and_line);
     }
 
-    sb8_printf(sb, " %S", ev.string);
+    sb8_printf(sb, " %S\n", ev.string);
     s8_t result = sb8_serial_end(sb);
-    core_print_message(result);
-    ma_end_scratch(scratch);
 
-    if (ev.level == log_level_fatal) {
-        if (core_desc.log.break_on_fatal) {
-#if PLATFORM_WINDOWS
-        if (IsDebuggerPresent())
-#endif
+    if (ev.level != log_level_fatal) {
+        IF_PLATFORM_WINDOWS(OutputDebugStringA(result.str);)
+        puts(result.str);
+    } else {
+        core_error_message(result.str);
+        #if PLATFORM_WASM
             debug_break();
-        } else {
-            SWITCH_PLATFORM_WINDOWS_WASM_ELSE(
-                ExitProcess(1),
-                debug_break(),
-                exit(1)
-            );
-        }
+        #else
+            if (core_desc.log.break_on_fatal) {
+                debug_break();
+            } else {
+                exit(1);
+            }
+        #endif
     }
+
+    ma_end_scratch(scratch);
 }
+
diff --git a/src/core/core_log.h b/src/core/core_log.h
index 6e1f0f9..a73e224 100644
--- a/src/core/core_log.h
+++ b/src/core/core_log.h
@@ -52,23 +52,27 @@ struct logger_t {
     b32 break_on_fatal;
 };
 
-fn void log_base(i32 module, log_level_t level, s8_t file_and_line, s8_t string);
-fn void log_basef(i32 module, log_level_t level, s8_t file_and_line, const char *str, ...);
-fn s8_t log_level_str(log_level_t level);
-
+///////////////////////////////
+// main api
 #define debugf(...) log_basef(module_null, log_level_debug, S8_FILE_AND_LINE, __VA_ARGS__)
 #define errorf(MODULE, ...) log_basef(MODULE, log_level_error, S8_FILE_AND_LINE, __VA_ARGS__)
 #define fatalf(...) (log_basef(module_null, log_level_fatal, S8_FILE_AND_LINE, __VA_ARGS__), 0)
 
-#define assert(x) (!(x) && fatalf("condition doesn't hold: " #x))
-#define assertf(x, ...) (!(x) && fatalf("condition doesn't hold: " __VA_ARGS__))
-
-#if PLATFORM_CL
-#define debug__break() __debugbreak()
+fn void core_error_message(char *str);
+#define program_version "---"
+#if PLATFORM_DEBUG_ASSERT
+#define assert(x) (!(x) && (core_error_message(FILE_AND_LINE ": internal program error! assertion failed, program version: " program_version), debug_break()))
 #else
-#define debug__break() __builtin_trap()
+#define assert(x) (void)(x)
 #endif
-#define debug_break() (debug__break(), 0)
+#define not_implemented assert(!"not implemented!")
+#define invalid_codepath assert(!"invalid code path!")
+
+
+
+fn void log_base(i32 module, log_level_t level, s8_t file_and_line, s8_t string);
+fn void log_basef(i32 module, log_level_t level, s8_t file_and_line, const char *str, ...);
+
 
 
 /*
diff --git a/src/core/core_platform_defines.h b/src/core/core_platform_defines.h
index c5d0128..fa41dca 100644
--- a/src/core/core_platform_defines.h
+++ b/src/core/core_platform_defines.h
@@ -64,6 +64,10 @@
 #define PLATFORM_ADDRESS_SANITIZER 0
 #endif
 
+#ifndef PLATFORM_DEBUG_ASSERT
+#define PLATFORM_DEBUG_ASSERT 1
+#endif
+
 #if PLATFORM_WINDOWS
 #define SWITCH_PLATFORM_WINDOWS_WASM_ELSE(WINDOWS, WASM, ELSE) WINDOWS
 #elif PLATFORM_WASM
@@ -72,7 +76,19 @@
 #define SWITCH_PLATFORM_WINDOWS_WASM_ELSE(WINDOWS, WASM, ELSE) ELSE
 #endif
 
-
 #if PLATFORM_CL
 #pragma warning(disable: 4116)
 #endif
+
+#if PLATFORM_CL
+#define debug__break() __debugbreak()
+#else
+#define debug__break() __builtin_trap()
+#endif
+#define debug_break() (debug__break(), 0)
+
+#if PLATFORM_WINDOWS
+#define IF_PLATFORM_WINDOWS(x) x
+#else
+#define IF_PLATFORM_WINDOWS(x)
+#endif
\ No newline at end of file
diff --git a/src/core/core_string.c b/src/core/core_string.c
index e4e8a21..fd3ca64 100644
--- a/src/core/core_string.c
+++ b/src/core/core_string.c
@@ -69,8 +69,8 @@ fn s8_t s8_from_char(char *string) {
 fn s16_t s16_from_s8(ma_arena_t *ma, s8_t string) {
     u16 *buffer = ma_push_array(ma, u16, string.len + 1);
     i64 len = wstr_from_str(buffer, string.len + 1, string.str, string.len);
-    assert(len < string.len);
-    return (s16_t){buffer,len};
+    assert(len <= string.len); // @todo: verify
+    return (s16_t){buffer, len};
 }
 
 fn s8_t s8_from_s16(ma_arena_t *ma, s16_t string) {
@@ -78,18 +78,15 @@ fn s8_t s8_from_s16(ma_arena_t *ma, s16_t string) {
     char *buffer = ma_push_array(ma, char, buffer_size);
     i64 len = str_from_wstr(buffer, buffer_size, string.str, string.len);
     assert(len < buffer_size);
-    return (s8_t){buffer,len};
+    return (s8_t){buffer, len};
 }
 
 fn s8_t s8_copy(ma_arena_t *ma, s8_t string) {
     char *copy = (char *)ma_push_size(ma, sizeof(char) * (string.len + 1));
-    if (copy) {
-        memory_copy(copy, string.str, string.len);
-        copy[string.len] = 0;
-        s8_t result = s8(copy, string.len);
-        return result;
-    }
-    return (s8_t){0};
+    memory_copy(copy, string.str, string.len);
+    copy[string.len] = 0;
+    s8_t result = s8(copy, string.len);
+    return result;
 }
 
 s8_t s8_copy_char(ma_arena_t *ma, char *s) {
@@ -207,8 +204,8 @@ s8_t s8_skip_past(s8_t string, s8_t a) {
 fn s8_t s8_slice(s8_t string, int64_t first_index, int64_t one_past_last_index) {
     if (one_past_last_index < 0) one_past_last_index = string.len + one_past_last_index + 1;
     if (first_index < 0) first_index = string.len + first_index;
-    assert(first_index < one_past_last_index && "s8_slice, first_index is bigger then one_past_last_index");
-    assert(string.len > 0 && "Slicing string of length 0! Might be an error!");
+    assert(first_index < one_past_last_index);
+    assert(string.len > 0);
     s8_t result = string;
     if (string.len > 0) {
         if (one_past_last_index > first_index) {
@@ -476,10 +473,7 @@ fn u64 u64_from_s8(s8_t s, u64 base) {
     u64 acc = 0;
     for (i64 i = 0; i < s.len; i++) {
         u64 num = u64_from_hexchar(s.str[i]);
-        if (num >= base) {
-            fatalf("failed to convert string into number, didn't expect: %c", s.str[i]);
-            break;
-        }
+        assert(num < base);
         acc *= base;
         acc += num;
     }
diff --git a/src/core/core_type_info.c b/src/core/core_type_info.c
index 810b394..c52a2f3 100644
--- a/src/core/core_type_info.c
+++ b/src/core/core_type_info.c
@@ -368,7 +368,8 @@ fn void ti__deserial_data_ex(ma_arena_t *arena, parser_t *par, void *p, type_t *
 
             lex_t *ident = parser_expect(par, lex_kind_ident);
             parser_expect(par, lex_kind_colon);
-            assert(s8_equal(ident->string, mem->name));
+
+            expect (s8_equal(ident->string, mem->name)) fatalf("expected identifier: %S, got instead %S", mem->name, ident->string);
 
             ti__deserial_data_ex(arena, par, mem_p, mem->type);
             parser_expect(par, lex_kind_comma);
diff --git a/src/wasm_app/main.c b/src/wasm_app/main.c
index 9acde2d..b639875 100644
--- a/src/wasm_app/main.c
+++ b/src/wasm_app/main.c
@@ -5,25 +5,24 @@
 // #include "debug.c"
 // #include "ui2.c"
 
-ma_arena_t *frame_arena;
-
+f64 delta_time;
 void app_update(ma_arena_t *perm_arena, app_event_t *events, i32 event_count) {
-    if (frame_arena == NULL) {
-        frame_arena = ma_push_arena(perm_arena, kib(32));
-    }
+    if (event_count) delta_time = events[0].delta_time;
+    draw_textf(v2f64(0,0), "delta time: %f", delta_time);
 
-    f64 pos = 0.0;
-    f64 offset = get_font_height() + 8;
-    for (i32 i = 0; i < event_count; i += 1) {
-        s8_t string = ti_serial_data(frame_arena, events + i, app_event_t);
-        sb8_t split = s8_split(frame_arena, string, s8_lit("\n"), s8_split_none);
+    ma_scratch_scope(temp) {
+        f64 offset = get_font_height() + 8;
+        f64 pos = offset;
+        for (i32 i = 0; i < event_count; i += 1) {
+            s8_t string = ti_serial_data(temp.arena, events + i, app_event_t);
+            sb8_t split = s8_split(temp.arena, string, s8_lit("\n"), s8_split_none);
 
-        for (sb8_node_t *it = split.first; it; it = it->next) {
-            draw_text((v2f64_t){0, pos}, white_color_global, it->string);
+            for (sb8_node_t *it = split.first; it; it = it->next) {
+                draw_text((v2f64_t){0, pos}, black_color_global, it->string);
 
-            pos += offset;
+                pos += offset;
+            }
         }
     }
 
-    ma_set0(frame_arena);
 }
diff --git a/todo.txt b/todo.txt
index 086f289..086ff7e 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,6 +1,7 @@
 [ ] platform
     [ ] app
         [ ] wasm
+            [x] exit function: maybe using alert
         [ ] win32
             [ ] hot reload / plugins
         [ ] linux
@@ -13,7 +14,7 @@
             [ ] revisit api
 
 [ ] core
-    [ ] revisit api
+    [x] revisit api
     [ ] s8_bin
         [ ] bin_write_begin - serialize binary data (sb8_bin_write?)
             bin_write_end