diff --git a/src/core/core.c b/src/core/core.c
index a4ced41..87a96d5 100644
--- a/src/core/core.c
+++ b/src/core/core.c
@@ -62,6 +62,7 @@
 #include "core_type_info.c"
 #include "core_hash.c"
 #include "core_hash_table.c"
+#include "core_array.c"
 #ifndef DONT_INCLUDE_GENERATED_MATH
 #include "core_math.gen.c"
 #endif
diff --git a/src/core/core.h b/src/core/core.h
index 7fc65a1..ae564b7 100644
--- a/src/core/core.h
+++ b/src/core/core.h
@@ -15,3 +15,4 @@
 #include "core_platform.h"
 #include "core_hash_table.h"
 #include "core_ctx.h"
+#include "core_array.h"
diff --git a/src/text_editor/core_array.c b/src/core/core_array.c
similarity index 53%
rename from src/text_editor/core_array.c
rename to src/core/core_array.c
index 046745c..510d233 100644
--- a/src/text_editor/core_array.c
+++ b/src/core/core_array.c
@@ -1,63 +1,3 @@
-typedef enum {
-    alokind_alloc,
-    alokind_dealloc,
-} alokind_t;
-
-typedef struct alo_t alo_t;
-struct alo_t {
-    void *object;
-    void *(*proc)(alo_t alo, alokind_t kind, void *ptr, size_t size);
-};
-
-fn void *arena_alo_proc(alo_t alo, alokind_t kind, void *ptr, size_t size) {
-    ma_arena_t *ma = alo.object;
-    if (kind == alokind_alloc) {
-        return ma_push_size(alo.object, size);
-    } else if (kind == alokind_dealloc) {
-        return NULL;
-    } else_is_invalid;
-    return NULL;
-}
-
-fn alo_t ma_alo(ma_arena_t *arena) {
-    return (alo_t){arena, arena_alo_proc};
-}
-
-fn alo_t ma_temp_alo(ma_temp_t temp) {
-    return ma_alo(temp.arena);
-}
-
-fn void dealloc(alo_t alo, void *ptr) {
-    alo.proc(alo, alokind_dealloc, ptr, 0);
-}
-
-fn void *alloc_size(alo_t alo, size_t size) {
-    return alo.proc(alo, alokind_alloc, NULL, size);
-}
-
-#define alloc_type(alo, type) (type *)alloc_size((aloc), sizeof(type))
-#define alloc_array(alo, type, count) (type *)alloc_size((alo), sizeof(type) * (count))
-
-#define array(type) struct { alo_t alo; type *data; i64 len; i64 cap; }
-typedef array(void) array_void_t;
-typedef array(i64) array_i64_t;
-
-#define arrisz(x) sizeof((x)->data[0])
-#define arrcst(x) ((array_void_t *)(x))
-#define array_init(a, this, count) (array__init((a), arrcst(this), arrisz(this), (count)))
-#define array_add(this, ...) (array__grow(arrcst(this), arrisz(this), 1), (this)->data[(this)->len++] = __VA_ARGS__)
-#define array_pop(this) (assert_expr((this)->len > 0), (this)->data[--(this)->len])
-#define array_dealloc(this) (dealloc((this)->alo, (this)->data))
-#define array_addn(this, n) (array__grow(arrcst(this), arrisz(this), (n)), (this)->len += (n), &(this)->data[(this)->len - (n)])
-#define array_insert(this, i, item) (array__insert(arrcst(this), arrisz(this), (i)), (this)->data[(i)] = (item))
-#define array_swapdel(this, i) (assert_expr((i) < (this)->len), (this)->data[(i)] = (this)->data[--(this)->len])
-#define array_del(this, i) (array__del(arrcst(this), arrisz(this), (i), 1))
-#define array_deln(this, i, count) (array__del(arrcst(this), arrisz(this), (i), (count)))
-#define array_copy(alo, dst, src) (array__copy((alo), arrcst(dst), (array_void_t *)(src), arrisz(dst)))
-#define array_last(x) ((x)->data[(x)->len - 1])
-
-#define array_for(type, it, array) for (type *it = (array)->data; it < (array)->data + (array)->len; it += 1)
-
 fn void array__init(alo_t alo, array_void_t *this, size_t item_size, i64 count) {
     assert(this->data == NULL);
     this->data = alloc_size(alo, item_size * count);
@@ -112,7 +52,7 @@ fn void array__insert(array_void_t *this, size_t item_size, i64 idx) {
 fn_test void test_array(void) {
     ma_temp_t scratch = ma_begin_scratch();
     {
-        array_i64_t arr = (array_i64_t){.alo = ma_temp_alo(scratch)};
+        array_i64_t arr = (array_i64_t){.alo = malot(scratch)};
         for (int i = 0; i < 512; i += 1) {
             array_add(&arr, i);
         }
@@ -130,7 +70,7 @@ fn_test void test_array(void) {
     }
 
     {
-        array_i64_t arr = (array_i64_t){.alo = ma_temp_alo(scratch)};
+        array_i64_t arr = (array_i64_t){.alo = malot(scratch)};
         i64 *i = array_addn(&arr, 10);
         assert(arr.len == 10 && arr.cap == 16);
         i64 *j = array_addn(&arr, 2);
@@ -140,7 +80,7 @@ fn_test void test_array(void) {
     }
 
     {
-        array_i64_t arr = (array_i64_t){.alo = ma_temp_alo(scratch)};
+        array_i64_t arr = (array_i64_t){.alo = malot(scratch)};
         for (int i = 0; i < 512; i += 1) {
             array_add(&arr, i);
         }
@@ -164,7 +104,7 @@ fn_test void test_array(void) {
         assert(arr.data[3] == 3);
 
         array_i64_t copy = {0};
-        array_copy(ma_temp_alo(scratch), &copy, &arr);
+        array_copy(malot(scratch), &copy, &arr);
         for (i64 i = 0; i < arr.len; i += 1) {
             assert(arr.data[i] == copy.data[i]);
         }
@@ -174,12 +114,3 @@ fn_test void test_array(void) {
 
     ma_end_scratch(scratch);
 }
-
-fn s16_t s16_alo_copy(alo_t ma, s16_t string) {
-    i64 byte_size = sizeof(u16) * string.len;
-    u16 *copy = (u16 *)alloc_size(ma, byte_size + sizeof(u16));
-    memory_copy(copy, string.str, byte_size);
-    copy[string.len] = 0;
-    s16_t result = s16_make(copy, string.len);
-    return result;
-}
diff --git a/src/core/core_array.h b/src/core/core_array.h
new file mode 100644
index 0000000..ed87e4d
--- /dev/null
+++ b/src/core/core_array.h
@@ -0,0 +1,24 @@
+#define array(type) struct { alo_t alo; type *data; i64 len; i64 cap; }
+typedef array(void) array_void_t;
+typedef array(i64) array_i64_t;
+
+#define arrisz(x) sizeof((x)->data[0])
+#define arrcst(x) ((array_void_t *)(x))
+#define array_init(a, this, count) (array__init((a), arrcst(this), arrisz(this), (count)))
+#define array_add(this, ...) (array__grow(arrcst(this), arrisz(this), 1), (this)->data[(this)->len++] = __VA_ARGS__)
+#define array_pop(this) (assert_expr((this)->len > 0), (this)->data[--(this)->len])
+#define array_dealloc(this) (dealloc((this)->alo, (this)->data))
+#define array_addn(this, n) (array__grow(arrcst(this), arrisz(this), (n)), (this)->len += (n), &(this)->data[(this)->len - (n)])
+#define array_insert(this, i, item) (array__insert(arrcst(this), arrisz(this), (i)), (this)->data[(i)] = (item))
+#define array_swapdel(this, i) (assert_expr((i) < (this)->len), (this)->data[(i)] = (this)->data[--(this)->len])
+#define array_del(this, i) (array__del(arrcst(this), arrisz(this), (i), 1))
+#define array_deln(this, i, count) (array__del(arrcst(this), arrisz(this), (i), (count)))
+#define array_copy(alo, dst, src) (array__copy((alo), arrcst(dst), (array_void_t *)(src), arrisz(dst)))
+#define array_last(x) ((x)->data[(x)->len - 1])
+#define array_for(type, it, array) for (type *it = (array)->data; it < (array)->data + (array)->len; it += 1)
+
+fn void array__init(alo_t alo, array_void_t *this, size_t item_size, i64 count);
+fn void array__copy(alo_t alo, array_void_t *dst, array_void_t *src, size_t item_size);
+fn void array__grow(array_void_t *this, size_t item_size, i64 item_count);
+fn void array__del(array_void_t *this, size_t item_size, i64 idx, i64 count);
+fn void array__insert(array_void_t *this, size_t item_size, i64 idx);
\ No newline at end of file
diff --git a/src/core/core_ctx.c b/src/core/core_ctx.c
index 998cb25..16f0813 100644
--- a/src/core/core_ctx.c
+++ b/src/core/core_ctx.c
@@ -11,4 +11,30 @@ gb_thread thread_ctx_t global_thread_context = {
 fn void core_init(void) {
     tcx = &global_thread_context;
     os_core_init();
-}
\ No newline at end of file
+}
+
+fn void *ma_arena_alo_proc(alo_t alo, alokind_t kind, void *ptr, size_t size) {
+    ma_arena_t *ma = alo.object;
+    if (kind == alokind_alloc) {
+        return ma_push_size(alo.object, size);
+    } else if (kind == alokind_dealloc) {
+        return NULL;
+    } else_is_invalid;
+    return NULL;
+}
+
+fn alo_t malo(ma_arena_t *arena) {
+    return (alo_t){arena, ma_arena_alo_proc};
+}
+
+fn alo_t malot(ma_temp_t temp) {
+    return malo(temp.arena);
+}
+
+fn void dealloc(alo_t alo, void *ptr) {
+    alo.proc(alo, alokind_dealloc, ptr, 0);
+}
+
+fn void *alloc_size(alo_t alo, size_t size) {
+    return alo.proc(alo, alokind_alloc, NULL, size);
+}
diff --git a/src/core/core_ctx.h b/src/core/core_ctx.h
index 2d3906f..25ac551 100644
--- a/src/core/core_ctx.h
+++ b/src/core/core_ctx.h
@@ -19,4 +19,22 @@ enum {
     tcx_slot_app,
 };
 
+typedef enum {
+    alokind_alloc,
+    alokind_dealloc,
+} alokind_t;
+
+typedef struct alo_t alo_t;
+struct alo_t {
+    void *object;
+    void *(*proc)(alo_t alo, alokind_t kind, void *ptr, size_t size);
+};
+
+#define alloc_type(alo, type) (type *)alloc_size((aloc), sizeof(type))
+#define alloc_array(alo, type, count) (type *)alloc_size((alo), sizeof(type) * (count))
+fn alo_t malo(ma_arena_t *arena);
+fn alo_t malot(ma_temp_t temp);
+fn void  dealloc(alo_t alo, void *ptr);
+fn void *alloc_size(alo_t alo, size_t size);
+
 gb_thread thread_ctx_t *tcx;
diff --git a/src/core/core_string16.c b/src/core/core_string16.c
index e718632..9edde9b 100644
--- a/src/core/core_string16.c
+++ b/src/core/core_string16.c
@@ -489,6 +489,15 @@ fn sb16_t s16_split(ma_arena_t *ma, s16_t string, s16_t find, s16_split_t flags)
     return result;
 }
 
+fn s16_t s16_copy_ex(alo_t ma, s16_t string) {
+    i64 byte_size = sizeof(u16) * string.len;
+    u16 *copy = (u16 *)alloc_size(ma, byte_size + sizeof(u16));
+    memory_copy(copy, string.str, byte_size);
+    copy[string.len] = 0;
+    s16_t result = s16_make(copy, string.len);
+    return result;
+}
+
 fn_test void test_string16(void) {
     ma_temp_t scratch = ma_begin_scratch();
 
diff --git a/src/testing/testing.gen.c b/src/testing/testing.gen.c
index 1149d7c..d58ccd4 100644
--- a/src/testing/testing.gen.c
+++ b/src/testing/testing.gen.c
@@ -1,8 +1,10 @@
 void test_string16(void);
 void test_hash_table(void);
 void test_intern_table(void);
+void test_array(void);
 fn void run_tests(void) {
     test_string16();
     test_hash_table();
     test_intern_table();
+    test_array();
 }
diff --git a/src/text_editor/text_editor_buffer.c b/src/text_editor/buffer16.c
similarity index 89%
rename from src/text_editor/text_editor_buffer.c
rename to src/text_editor/buffer16.c
index 94346f9..9adc33d 100644
--- a/src/text_editor/text_editor_buffer.c
+++ b/src/text_editor/buffer16.c
@@ -1,74 +1,57 @@
 #define BUFFER_DEBUG 1
 
-typedef struct caret_t caret_t;
-struct caret_t {
-    i64 ifront;
-    union {
-        r1i64_t range;
-        i64 pos[2];
-    };
-};
-
-typedef struct xy_t xy_t;
-struct xy_t {
-    i64 col;
-    i64 line;
-};
-
-typedef struct edit16_t edit16_t;
-struct edit16_t {
-    r1i64_t range;
-    s16_t string;
-};
-
-// @todo: redo tree
-typedef array(edit16_t) array_edit16_t;
-typedef array(caret_t) array_caret_t;
-typedef struct history16_t history16_t;
-struct history16_t {
-    array_edit16_t edits;
-    array_caret_t carets;
-};
-
-typedef array(history16_t) array_history16_t;
-typedef struct buffer16_id_t buffer16_id_t;
-struct buffer16_id_t { i64 e; };
-
-typedef struct buffer16_t buffer16_t;
-struct buffer16_t {
-    s8_t name;
-    buffer16_id_t id;
-
-    i32 change_id;
-    i8 edit_phase;
-
-    struct {
-        b8 dirty: 1;
-        b8 history: 1;
-        b8 line_starts: 1;
-    } flags;
-
-    union {
-        s16_t string;
-        u16 *data;
-        struct {
-            u16 *str;
-            i64  len;
-        };
-    };
-    i64 cap;
-    array_i64_t line_starts;
-
-    array_history16_t undo_stack;
-    array_history16_t redo_stack;
-    alo_t alo;
-};
-
 gb i64 buffer_raw_ids;
-const b32 dont_kill_selection = false;
-const b32 kill_selection = true;
 
-fn void buffer16_multi_cursor_apply_edits(buffer16_t *buffer, array_edit16_t edits);
+
+///////////////////////////////
+// caret helpers
+///////////////////////////////
+
+fn i64 caret_get_front(caret_t caret) {
+    i64 result = caret.pos[caret.ifront];
+    return result;
+}
+
+fn i64 caret_get_back(caret_t caret) {
+    i64 result = caret.pos[(caret.ifront + 1) % 2];
+    return result;
+}
+
+fn caret_t caret_make(i64 front, i64 back) {
+    caret_t result = {0};
+    if (front >= back) {
+        result.range.min = back;
+        result.range.max = front;
+        result.ifront = 1;
+    } else {
+        result.range.min = front;
+        result.range.max = back;
+        result.ifront = 0;
+    }
+    return result;
+}
+
+fn caret_t caret_set_front(caret_t caret, i64 pos) {
+    i64 back = caret_get_back(caret);
+    caret_t result = caret_make(pos, back);
+    return result;
+}
+
+fn caret_t caret_set_back(caret_t caret, i64 pos) {
+    i64 front = caret_get_front(caret);
+    caret_t result = caret_make(front, pos);
+    return result;
+}
+
+fn b32 carets_are_equal(caret_t a, caret_t b) {
+    b32 result = r1i64_are_equal(a.range, b.range) && a.ifront == b.ifront;
+    return result;
+}
+
+fn b32 carets_overlap(caret_t a, caret_t b) {
+    b32 result = r1i64_overlap(a.range, b.range);
+    return result;
+}
 
 ///////////////////////////////
 // buffer helpers
@@ -181,47 +164,6 @@ fn r1i64_t buffer16_clamp_range(buffer16_t *buffer, r1i64_t range) {
     return result;
 }
 
-fn i64 caret_get_front(caret_t caret) {
-    i64 result = caret.pos[caret.ifront];
-    return result;
-}
-
-fn i64 caret_get_back(caret_t caret) {
-    i64 result = caret.pos[(caret.ifront + 1) % 2];
-    return result;
-}
-
-fn caret_t caret_make(i64 front, i64 back) {
-    caret_t result = {0};
-    if (front >= back) {
-        result.range.min = back;
-        result.range.max = front;
-        result.ifront = 1;
-    } else {
-        result.range.min = front;
-        result.range.max = back;
-        result.ifront = 0;
-    }
-    return result;
-}
-
-fn caret_t caret_set_front(caret_t caret, i64 pos) {
-    i64 back = caret_get_back(caret);
-    caret_t result = caret_make(pos, back);
-    return result;
-}
-
-fn caret_t caret_set_back(caret_t caret, i64 pos) {
-    i64 front = caret_get_front(caret);
-    caret_t result = caret_make(front, pos);
-    return result;
-}
-
-fn b32 carets_are_equal(caret_t a, caret_t b) {
-    b32 result = r1i64_are_equal(a.range, b.range) && a.ifront == b.ifront;
-    return result;
-}
-
 fn i64 buffer16_get_word_start(buffer16_t *buffer, i64 pos) {
     pos = CLAMP(pos, (i64)0, buffer->len);
     for (i64 i = pos - 1; i >= 0; i -= 1) {
@@ -257,7 +199,7 @@ fn i64 buffer16_get_next_word_end(buffer16_t *buffer, i64 pos) {
         // semantics - proper max is one past last index
         if (!(i < buffer->len))
             break;
-        fn if (prev == L'\n' || (prev && prev != buffer->str[i]) || char16_is_word(buffer->str[i])) {
+        if (prev == L'\n' || (prev && prev != buffer->str[i]) || char16_is_word(buffer->str[i])) {
             break;
         }
         prev = buffer->str[i];
@@ -271,7 +213,7 @@ fn i64 buffer16_get_prev_word_start(buffer16_t *buffer, i64 pos) {
     u16 prev = 0;
     i64 i    = pos - 1;
     for (; i >= 0; i -= 1) {
-        fn if (prev == L'\n' || (prev && prev != buffer->str[i]) || char16_is_word(buffer->str[i])) {
+        if (prev == L'\n' || (prev && prev != buffer->str[i]) || char16_is_word(buffer->str[i])) {
             break;
         }
         pos  = i;
@@ -332,20 +274,6 @@ fn i64 buffer16_offset_pos_by_line(buffer16_t *buffer, i64 pos, i64 line_offset)
 // raw buffer operations
 ///////////////////////////////
 
-fn void buffer16_raw_init(alo_t alo, buffer16_t *buffer, s8_t name, i64 size) {
-    buffer->id = (buffer16_id_t){++buffer_raw_ids};
-    buffer->name = name;
-    buffer->alo = alo;
-    buffer->cap = size;
-    buffer->data = alloc_array(alo, u16, size);
-    array_init(alo, &buffer->line_starts, 128);
-    array_init(alo, &buffer->undo_stack, 128);
-    array_init(alo, &buffer->redo_stack, 128);
-    buffer->flags.line_starts = true;
-    buffer->flags.history = true;
-    array_add(&buffer->line_starts, 0);
-}
-
 fn void buffer16_raw_grow(buffer16_t *buffer, i64 change_size) {
     i64 new_size = buffer->len + change_size;
     if (new_size > buffer->cap) {
@@ -453,6 +381,32 @@ fn void buffer16_raw_replace_text(buffer16_t *buffer, r1i64_t range, s16_t strin
 #endif
 }
 
+///////////////////////////////
+// buffer multicursor + history
+///////////////////////////////
+
+fn void buffer16_init(alo_t alo, buffer16_t *buffer, s8_t name, i64 size) {
+    buffer->id = (buffer16_id_t){++buffer_raw_ids};
+    buffer->name = name;
+    buffer->alo = alo;
+    buffer->cap = size;
+    buffer->data = alloc_array(alo, u16, size);
+    array_init(alo, &buffer->line_starts, 128);
+    array_init(alo, &buffer->undo_stack, 128);
+    array_init(alo, &buffer->redo_stack, 128);
+    buffer->flags.line_starts = true;
+    buffer->flags.history = true;
+    array_add(&buffer->line_starts, 0);
+}
+
+fn void buffer16_deinit(buffer16_t *buffer) {
+    // @todo: verify this works
+    array_dealloc(&buffer->line_starts);
+    dealloc(buffer->alo, buffer->data);
+    buffer16_dealloc_history_array(buffer, &buffer->undo_stack);
+    buffer16_dealloc_history_array(buffer, &buffer->redo_stack);
+}
+
 fn void buffer16_save_history_before_merge_cursor(buffer16_t *buffer, array_history16_t *stack, array_caret_t *carets) {
     if (!buffer->flags.history) {
         return;
@@ -473,24 +427,25 @@ fn void buffer16_save_history_before_apply_edits(buffer16_t *buffer, array_histo
 
     // make reverse edits
     array_for(edit16_t, it, &entry->edits) {
-        it->range = (r1i64_t){it->range.min, it->range.min + it->string.len};
-        it->string = s16_alo_copy(buffer->alo, buffer16_get_string(buffer, it->range));
+        r1i64_t new_range = {it->range.min, it->range.min + it->string.len};
+        s16_t string = buffer16_get_string(buffer, it->range);
+        it->string = s16_copy_ex(buffer->alo, string);
+        it->range = new_range;
     }
 
     ma_temp_t scratch = ma_begin_scratch1(buffer->alo.object);
     array_edit16_t temp_edit = {0};
-    array_copy(ma_temp_alo(scratch), &temp_edit, &entry->edits);
+    array_copy(malot(scratch), &temp_edit, &entry->edits);
 
     // fix reverse edits
-    for (int i = 0; i < edits->len; i += 1) {
-        edit16_t *it = edits->data + i;
-        i64 remove_size = r1i64_size(it->range);
-        i64 insert_size = it->string.len;
+    array_for(edit16_t, edit, edits) {
+        i64 remove_size = r1i64_size(edit->range);
+        i64 insert_size = edit->string.len;
         i64 offset = insert_size - remove_size;
-        for (int j = 0; j < entry->edits.len; j += 1) {
+        for (i64 i = 0; i < entry->edits.len; i += 1) {
             edit16_t *new_edit = entry->edits.data + i;
             edit16_t *old_edit = temp_edit.data + i;
-            if (old_edit->range.min > it->range.min) {
+            if (old_edit->range.min > edit->range.min) {
                 new_edit->range.min += offset;
                 new_edit->range.max += offset;
             }
@@ -520,11 +475,12 @@ fn void buffer16_redo_edit(buffer16_t *buffer, array_caret_t *carets) {
 }
 
 fn void buffer16_undo_edit(buffer16_t *buffer, array_caret_t *carets) {
-    if (!buffer->flags.history || buffer->redo_stack.len <= 0) {
+    if (!buffer->flags.history || buffer->undo_stack.len <= 0) {
         return;
     }
 
     history16_t entry = array_pop(&buffer->undo_stack);
+
     buffer16_save_history_before_merge_cursor(buffer, &buffer->redo_stack, carets);
     buffer16_save_history_before_apply_edits(buffer, &buffer->redo_stack, &entry.edits);
     buffer16_multi_cursor_apply_edits(buffer, entry.edits);
@@ -557,10 +513,6 @@ fn void buffer16_dealloc_history_entries(buffer16_t *buffer, array_history16_t *
 }
 
 
-fn void buffer16_clear_redo_stack(buffer16_t *buffer) {
-    buffer16_dealloc_history_entries(buffer, &buffer->redo_stack);
-}
-
 fn void buffer16_dealloc_history_array(buffer16_t *buffer, array_history16_t *entries) {
     buffer16_dealloc_history_entries(buffer, entries);
     array_dealloc(entries);
@@ -575,7 +527,7 @@ fn array_edit16_t buffer16_begin_edit(alo_t alo, buffer16_t *buffer, array_caret
         buffer->edit_phase += 1;
         assert(carets->len);
         buffer16_save_history_before_merge_cursor(buffer, &buffer->undo_stack, carets);
-        buffer16_clear_redo_stack(buffer);
+        buffer16_dealloc_history_entries(buffer, &buffer->redo_stack);
     }
     array_edit16_t edits = (array_edit16_t){.alo = alo};
     return edits;
@@ -596,7 +548,7 @@ fn void buffer16_adjust_carets(array_edit16_t *edits, array_caret_t *carets) {
     assert(edits->alo.object == carets->alo.object);
 
     array_caret_t new_carets = {0};
-    array_copy(ma_temp_alo(scratch), &new_carets, carets);
+    array_copy(malot(scratch), &new_carets, carets);
     array_for(edit16_t, it, edits) {
         i64 remove_size = r1i64_size(it->range);
         i64 insert_size = it->string.len;
@@ -643,7 +595,7 @@ fn void buffer16_end_edit(buffer16_t *buffer, array_edit16_t *edits, array_caret
     assert(buffer->alo.object == edits->alo.object);
 
     array_caret_t new_carets = {0};
-    array_copy(ma_temp_alo(scratch), &new_carets, carets);
+    array_copy(malot(scratch), &new_carets, carets);
     array_for(edit16_t, it, edits) {
         i64 remove_size = r1i64_size(it->range);
         i64 insert_size = it->string.len;
@@ -679,7 +631,7 @@ fn void buffer16_end_edit(buffer16_t *buffer, array_edit16_t *edits, array_caret
     ma_end_scratch(scratch);
 }
 
-void caret_merge_sort(i64 Count, caret_t *First, caret_t *Temp) {
+fn void caret_merge_sort(i64 Count, caret_t *First, caret_t *Temp) {
     // SortKey = range.min
     if (Count == 1) {
         // NOTE(casey): No work to do.
@@ -733,7 +685,7 @@ void caret_merge_sort(i64 Count, caret_t *First, caret_t *Temp) {
     }
 }
 
-void edit16_merge_sort(i64 Count, edit16_t *First, edit16_t *Temp) {
+fn void edit16_merge_sort(i64 Count, edit16_t *First, edit16_t *Temp) {
     // SortKey = range.min
     if (Count == 1) {
         // NOTE(casey): No work to do.
@@ -814,7 +766,7 @@ fn void buffer16_multi_cursor_apply_edits(buffer16_t *buffer, array_edit16_t edi
     {
         ma_temp_t scratch = ma_begin_scratch1(buffer->alo.object);
         array_edit16_t edits_copy = {0};
-        array_copy(ma_temp_alo(scratch), &edits_copy, &edits);
+        array_copy(malot(scratch), &edits_copy, &edits);
         if (edits.len > 1) edit16_merge_sort(edits.len, edits_copy.data, edits.data);
         edits = edits_copy;
         ma_end_scratch(scratch);
@@ -854,7 +806,7 @@ fn void buffer16_merge_carets(buffer16_t *buffer, array_caret_t *carets) {
 
     ma_temp_t scratch = ma_begin_scratch1(buffer->alo.object);
     array_caret_t c1 = {0};
-    array_copy(ma_temp_alo(scratch), &c1, carets);
+    array_copy(malot(scratch), &c1, carets);
     if (carets->len > 1) {
         caret_merge_sort(carets->len, c1.data, carets->data);
     }
@@ -887,7 +839,7 @@ fn_test void buffer16_test(void) {
     {
         s16_t string = s16("thing itself");
         buffer16_t *buffer = ma_push_type(scratch.arena, buffer16_t);
-        buffer16_raw_init(ma_temp_alo(scratch), buffer, S8_FILE_AND_LINE, 16);
+        buffer16_init(malot(scratch), buffer, S8_FILE_AND_LINE, 16);
         buffer16_raw_replace_text(buffer, r1i64_null, string);
         assert(s16_are_equal(buffer->string, string));
         assert(buffer->cap == 16);
@@ -919,7 +871,7 @@ fn_test void buffer16_test(void) {
     {
         s16_t string = s16("thing itself_and meme");
         buffer16_t *buffer = ma_push_type(scratch.arena, buffer16_t);
-        buffer16_raw_init(ma_temp_alo(scratch), buffer, S8_FILE_AND_LINE, 10);
+        buffer16_init(malot(scratch), buffer, S8_FILE_AND_LINE, 10);
         buffer16_raw_replace_text(buffer, r1i64_null, string);
         r1i64_t range = buffer16_enclose_word(buffer, 18);
         buffer16_raw_replace_text(buffer, range, s16("cat"));
@@ -934,7 +886,7 @@ fn_test void buffer16_test(void) {
 
     {
         buffer16_t *buffer = ma_push_type(scratch.arena, buffer16_t);
-        buffer16_raw_init(ma_temp_alo(scratch), buffer, S8_FILE_AND_LINE, 16);
+        buffer16_init(malot(scratch), buffer, S8_FILE_AND_LINE, 16);
         for (int i = 0; i < 16; i += 1) {
             buffer16_raw_replace_text(buffer, r1i64_null, s16("line of memes\n"));
         }
@@ -942,14 +894,15 @@ fn_test void buffer16_test(void) {
     }
 
     {
-
+        s16_t string = s16("some thing or another and stuff like that");
+        s16_t meme_string = s16("meme meme or another and stuff like that");
         buffer16_t *buffer = ma_push_type(scratch.arena, buffer16_t);
-        buffer16_raw_init(ma_temp_alo(scratch), buffer, S8_FILE_AND_LINE, 128);
-        buffer16_raw_replace_text(buffer, r1i64_null, s16("some thing or another and stuff like that"));
+        buffer16_init(malot(scratch), buffer, S8_FILE_AND_LINE, 128);
+        buffer16_raw_replace_text(buffer, r1i64_null, string);
 
         {
             array_caret_t carets = {0};
-            array_init(ma_temp_alo(scratch), &carets, 32);
+            array_init(malot(scratch), &carets, 32);
             array_add(&carets, caret_make(0, 4));
             array_add(&carets, caret_make(3, 8));
             array_add(&carets, caret_make(3, 8));
@@ -964,12 +917,12 @@ fn_test void buffer16_test(void) {
 
         {
             array_caret_t carets = {0};
-            array_init(ma_temp_alo(scratch), &carets, 32);
+            array_init(malot(scratch), &carets, 32);
             array_add(&carets, caret_make(0, 4));
             array_add(&carets, caret_make(0, 3));
             array_add(&carets, caret_make(5, 10));
 
-            array_edit16_t edits = buffer16_begin_edit(ma_temp_alo(scratch), buffer, &carets);
+            array_edit16_t edits = buffer16_begin_edit(malot(scratch), buffer, &carets);
 
             buffer16_merge_carets(buffer, &carets);
             assert(carets.len == 2);
@@ -979,7 +932,14 @@ fn_test void buffer16_test(void) {
             }
 
             buffer16_end_edit(buffer, &edits, &carets, kill_selection);
-            assert(s16_are_equal(buffer->string, s16("meme meme or another and stuff like that")));
+            assert(s16_are_equal(buffer->string, meme_string));
+
+            for (i32 i = 0; i < 32; i += 1) {
+                buffer16_undo_edit(buffer, &carets);
+                assert(s16_are_equal(buffer->string, string));
+                buffer16_redo_edit(buffer, &carets);
+                assert(s16_are_equal(buffer->string, meme_string));
+            }
         }
     }
 
diff --git a/src/text_editor/buffer16.h b/src/text_editor/buffer16.h
new file mode 100644
index 0000000..bb58012
--- /dev/null
+++ b/src/text_editor/buffer16.h
@@ -0,0 +1,129 @@
+typedef struct caret_t caret_t;
+struct caret_t {
+    i64 ifront;
+    union {
+        r1i64_t range;
+        i64 pos[2];
+    };
+};
+
+typedef struct xy_t xy_t;
+struct xy_t {
+    i64 col;
+    i64 line;
+};
+
+typedef struct edit16_t edit16_t;
+struct edit16_t {
+    r1i64_t range;
+    s16_t string;
+};
+
+// @todo: redo tree
+typedef array(edit16_t) array_edit16_t;
+typedef array(caret_t) array_caret_t;
+typedef struct history16_t history16_t;
+struct history16_t {
+    array_edit16_t edits;
+    array_caret_t carets;
+};
+
+typedef array(history16_t) array_history16_t;
+typedef struct buffer16_id_t buffer16_id_t;
+struct buffer16_id_t { i64 e; };
+
+typedef struct buffer16_t buffer16_t;
+struct buffer16_t {
+    s8_t name;
+    buffer16_id_t id;
+
+    i32 change_id;
+    i8 edit_phase;
+
+    struct {
+        b8 dirty: 1;
+        b8 history: 1;
+        b8 line_starts: 1;
+    } flags;
+
+    union {
+        s16_t string;
+        u16 *data;
+        struct {
+            u16 *str;
+            i64  len;
+        };
+    };
+    i64 cap;
+    array_i64_t line_starts;
+
+    array_history16_t undo_stack;
+    array_history16_t redo_stack;
+    alo_t alo;
+};
+
+const b32 dont_kill_selection = false;
+const b32 kill_selection = true;
+
+
+///////////////////////////////
+// caret helpers
+fn caret_t        caret_make(i64 front, i64 back);
+fn i64            caret_get_front(caret_t caret);
+fn i64            caret_get_back(caret_t caret);
+fn caret_t        caret_set_front(caret_t caret, i64 pos);
+fn caret_t        caret_set_back(caret_t caret, i64 pos);
+fn b32            carets_are_equal(caret_t a, caret_t b);
+fn b32            carets_overlap(caret_t a, caret_t b);
+
+///////////////////////////////
+// buffer helpers
+fn i64            buffer16_pos_to_line(buffer16_t *buffer, i64 pos);
+fn r1i64_t        buffer16_get_line_range(buffer16_t *buffer, i64 line);
+fn r1i64_t        buffer16_get_line_range_full(buffer16_t *buffer, i64 line, i64 *eof);
+fn xy_t           buffer16_pos_to_xy(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_xy_to_pos(buffer16_t *buffer, xy_t xy);
+fn i64            buffer16_xy_to_pos_without_new_line(buffer16_t *buffer, xy_t xy);
+fn s16_t          buffer16_get_string(buffer16_t *buffer, r1i64_t range);
+fn s16_t          buffer16_get_line_string(buffer16_t *buffer, i64 line);
+fn r1i64_t        buffer16_get_range_end(buffer16_t *buffer);
+fn r1i64_t        buffer16_get_range(buffer16_t *buffer);
+fn i64            buffer16_clamp_pos(buffer16_t *buffer, i64 pos);
+fn r1i64_t        buffer16_clamp_range(buffer16_t *buffer, r1i64_t range);
+fn i64            buffer16_get_word_start(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_get_word_end(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_get_next_word_end(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_get_prev_word_start(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_get_line_start(buffer16_t *buffer, i64 pos, i64 *eof);
+fn i64            buffer16_get_line_end(buffer16_t *buffer, i64 pos, i64 *eof);
+fn i64            buffer16_get_line_start_full(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_get_line_end_full(buffer16_t *buffer, i64 pos);
+fn r1i64_t        buffer16_enclose_word(buffer16_t *buffer, i64 pos);
+fn u16            buffer16_get_char(buffer16_t *buffer, i64 pos);
+fn i64            buffer16_offset_pos_by_line(buffer16_t *buffer, i64 pos, i64 line_offset);
+
+///////////////////////////////
+// buffer raw textural operations. no history
+fn void           buffer16_raw_grow(buffer16_t *buffer, i64 change_size);
+fn void           buffer16_raw_replace_text(buffer16_t *buffer, r1i64_t range, s16_t string);
+
+///////////////////////////////
+// buffer multicursor + history
+fn void           buffer16_init(alo_t alo, buffer16_t *buffer, s8_t name, i64 size);
+fn void           buffer16_deinit(buffer16_t *buffer);
+fn void           buffer16_add_edit(array_edit16_t *edits, r1i64_t range, s16_t string);
+fn array_edit16_t buffer16_begin_edit(alo_t alo, buffer16_t *buffer, array_caret_t *carets);
+fn void           buffer16_end_edit(buffer16_t *buffer, array_edit16_t *edits, array_caret_t *carets, b32 kill_selection);
+fn void           buffer16_merge_carets(buffer16_t *buffer, array_caret_t *carets);
+fn void           buffer16_adjust_carets(array_edit16_t *edits, array_caret_t *carets);
+
+fn void           buffer16_redo_edit(buffer16_t *buffer, array_caret_t *carets);
+fn void           buffer16_undo_edit(buffer16_t *buffer, array_caret_t *carets);
+
+fn void           buffer16_save_history_before_merge_cursor(buffer16_t *buffer, array_history16_t *stack, array_caret_t *carets);
+fn void           buffer16_save_history_before_apply_edits(buffer16_t *buffer, array_history16_t *stack, array_edit16_t *edits);
+fn void           buffer16_pre_begin_edit_save_caret_history(buffer16_t *buffer, array_caret_t *carets);
+
+fn void           buffer16_dealloc_history_entries(buffer16_t *buffer, array_history16_t *entries);
+fn void           buffer16_dealloc_history_array(buffer16_t *buffer, array_history16_t *entries);
+fn void           buffer16_multi_cursor_apply_edits(buffer16_t *buffer, array_edit16_t edits);
diff --git a/src/text_editor/text_editor_main.c b/src/text_editor/text_editor_main.c
index 5e20589..6ade677 100644
--- a/src/text_editor/text_editor_main.c
+++ b/src/text_editor/text_editor_main.c
@@ -2,6 +2,7 @@
 #include "os/os.h"
 #include "app/app.h"
 #include "profiler/profiler.h"
+#include "buffer16.h"
 // #include "ui/ui.h"
 
 
@@ -10,8 +11,7 @@
 #include "app/app.c"
 #include "profiler/profiler.c"
 #include "render/render.c"
-#include "core_array.c"
-#include "text_editor_buffer.c"
+#include "buffer16.c"
 // #include "ui/ui.c"
 
 #include "text_editor.gen.c"
diff --git a/src/ui/ui.c b/src/ui/ui.c
index 281c23f..2af5ff8 100644
--- a/src/ui/ui.c
+++ b/src/ui/ui.c
@@ -367,7 +367,7 @@ fn ui_signal_t ui_signal_from_box(ui_box_t *box) {
 }
 
 fn v2f32_t ui_aligned_text_pos(f32 offset, ui_text_align_t text_align, r2f32_t rect, s8_t string, v2f32_t string_size) {
-    v2f32_t rect_size = r2f32_get_size(rect);
+    v2f32_t rect_size = r2f32_size(rect);
     v2f32_t rect_string_diff = v2f32_sub(rect_size, string_size);
     v2f32_t center_pos = v2f32_divs(rect_string_diff, 2);
     v2f32_t pos_in_rect = v2f32(0, center_pos.y);
@@ -390,7 +390,7 @@ struct ui_draw_compute_t {
 fn r2f32_t ui_get_appear_rect(ui_box_t *box) {
     r2f32_t result = box->rect;
     if (box->flags.animate_appear && !ui_id_is_null(box->id)) {
-        v2f32_t size = v2f32_muls(r2f32_get_size(result), 0.15f);
+        v2f32_t size = v2f32_muls(r2f32_size(result), 0.15f);
         r2f32_t smaller_rect = r2f32_shrink(result, size);
         f32 appear_t = f32_ease_out_n(f32_clamp01(box->appear_t * 2), 10);
         result = r2f32_lerp(smaller_rect, result, appear_t);
@@ -634,7 +634,7 @@ fn void ui_tree_table_begin(ui_code_loc_t loc) {
 fn void ui_tree_table_end(void) {
     ui_box_t *box = ui_pop_top();
     ui_set_children_sums(box);
-    ui_next_rect(ui_top_lop(), ui_top_rectp(), r2f32_get_size(box->rect));
+    ui_next_rect(ui_top_lop(), ui_top_rectp(), r2f32_size(box->rect));
 }
 
 #define ui_tree_table_expandable(...) defer_if (ui_tree_table_push_expandable(UILOC, __VA_ARGS__).clicked, ui_tree_table_pop_expandable())
@@ -998,7 +998,7 @@ struct ui_scroller_t {
 
 fn void ui_scroller_calc_vertical(ui_scroller_t s) {
     ui_set_top(s.verti.box) {
-        f32 scroller_rect_pixels = r2f32_get_size(s.verti.box->rect).y;
+        f32 scroller_rect_pixels = r2f32_size(s.verti.box->rect).y;
         f32 all_items_size = s.p.verti.max_size;
         f32 scroller_size = f32_clamp01(s.verti.item_box_pixels / (all_items_size + s.verti.item_box_pixels));
         f32 scrollable_space = (1 - scroller_size);
@@ -1023,7 +1023,7 @@ fn void ui_scroller_calc_vertical(ui_scroller_t s) {
         }
         if (upper_box_signal.dragging || down_box_signal.dragging) {
             s.p.verti.value[0] = (ev->mouse_pos.y - upper_box->rect.min.y) * coef;
-            s.p.verti.value[0] -= (r2f32_get_size(slider_box->rect).y / 2) * coef;
+            s.p.verti.value[0] -= (r2f32_size(slider_box->rect).y / 2) * coef;
         }
         if (ev->kind == app_event_kind_mouse_wheel) {
             s.p.verti.value[0] -= ev->mouse_wheel_delta.y;
@@ -1038,7 +1038,7 @@ fn ui_scroller_t ui_begin_scroller(ui_code_loc_t loc, ui_scroller_params_t p) {
     if (p.verti.enabled) {
         s.verti.box = ui_box(.loc = loc, .rect = r2f32_cut_right(&p.parent->rect, ui_dm(0.5f)), .flags = {.draw_rect = true});
         r2f32_cut_bottom(&s.verti.box->rect, ui_dm(0.5f));
-        s.verti.item_box_pixels = r2f32_get_size(p.parent->rect).y;
+        s.verti.item_box_pixels = r2f32_size(p.parent->rect).y;
         if (p.verti.item_count) {
             s.p.verti.max_size = s.p.verti.item_pixels * s.p.verti.item_count;
             ui_scroller_calc_vertical(s);
@@ -1077,7 +1077,7 @@ fn void ui_end_scroller(ui_scroller_t s) {
 
     if (s.p.hori.enabled) {
         ui_set_top(s.hori.box) {
-            f32 scroller_rect_pixels = r2f32_get_size(s.hori.box->rect).x;
+            f32 scroller_rect_pixels = r2f32_size(s.hori.box->rect).x;
             f32 scroller_button_size_norm = f32_clamp01(scroller_rect_pixels / s.p.hori.max_size);
             f32 scrollable_space = (1.f - scroller_button_size_norm);
 
@@ -1101,7 +1101,7 @@ fn void ui_end_scroller(ui_scroller_t s) {
             }
             if (left_box_sig.dragging || right_box_sig.dragging) {
                 s.p.hori.value[0] = (ev->mouse_pos.x - left_box->rect.min.x) * coef;
-                s.p.hori.value[0] -= (r2f32_get_size(slider_box->rect).x / 2) * coef;
+                s.p.hori.value[0] -= (r2f32_size(slider_box->rect).x / 2) * coef;
             }
             if (ev->kind == app_event_kind_mouse_wheel) {
                 s.p.hori.value[0] -= ev->mouse_wheel_delta.x;
@@ -1399,7 +1399,7 @@ fn void ui_demo_update(app_frame_t *frame, mt_tweak_t *tweak_table, i32 tweak_co
                 ui_serial_type(UILOC, &ui_test_event, type(app_event_t));
 
                 r2f32_t scroll_rect = r2f32_fix(ui_top_rect());
-                scroller.p.verti.max_size = r2f32_get_size(scroll_rect).y;
+                scroller.p.verti.max_size = r2f32_size(scroll_rect).y;
             }
 
             ui_end_scroller(scroller);
diff --git a/src/wasm_app/wasm_app.gen.c b/src/wasm_app/wasm_app.gen.c
index 4d1fab2..37bc685 100644
--- a/src/wasm_app/wasm_app.gen.c
+++ b/src/wasm_app/wasm_app.gen.c
@@ -10,5 +10,6 @@ void run_all_tests(void) {
     test_string16();
     test_hash_table();
     test_intern_table();
+    test_array();
     ui_test_text_replace();
 }// run_all_tests()