diff --git a/README.md b/README.md
index f9c43b6..d6d8772 100644
--- a/README.md
+++ b/README.md
@@ -27,7 +27,8 @@ of making the region of memory allocated to more explicit.
 operations are included by default.
 - [x] Generic data-structures. The premier one is the
 [Dynamic Array](https://dylanfalconer.com/articles/dynamic-arrays-in-c), which
-brings the power of C++'s `std::vector` to C. 
+brings the power of C++'s `std::vector` to C. There is also a HashMap, which is
+implemented as a [4-ary hash-trie](https://nullprogram.com/blog/2023/09/30/).
 - [x] A I/O system that supports both standard input/output and file
 input/output. It's built on a basic buffer type that you can flush to output
 data. This buffer type also acts as a **string builder**, by letting you append
@@ -38,6 +39,7 @@ primitives.
 - [ ] A 3D Math API with supports for Vectors and Matricies using SIMD.
 - [ ] A simple GUI initialization system that gets you a window with immediate-mode
 input and a Direct3D11 (Win32) / OpenGL (Linux) context to build a renderer with.
+- [ ] A simple immediate mode GUI with support for custom widgets.
 - [ ] An audio library. Windows implementation uses WASAPI, Linux uses ALSA.
 
 ---
diff --git a/bastd/examples/data_structs.c b/bastd/examples/data_structs.c
new file mode 100644
index 0000000..f60d79c
--- /dev/null
+++ b/bastd/examples/data_structs.c
@@ -0,0 +1,89 @@
+#define BASTD_CLI
+#include "../../bastd.c"
+
+/* The sl_TYPE macro defines the type of the generic. It is cleared after every
+   include of "../slice.c"
+*/
+#define sl_TYPE I64
+#include "../slice.c"
+
+
+// SLICE types
+FUNCTION void
+fib_slice(Buffer *output, m_Allocator *perm)
+{
+	// Slices can be created with a backing array to start with.
+	I64 init[] = {0, 1};
+	sl_I64 fib = sl_I64_create(init, 2);
+
+	for (;;) {
+		// The data in a slice can be accessed like a normal array
+		I64 a = fib.elems[fib.len - 2];
+		I64 b = fib.elems[fib.len - 1];
+		if (a + b > 255) {
+			break;
+		}
+
+		/* The sl_TYPE_push function automatically doubles the capacity of the
+		   array if the slice is full and returns a pointer to a new element
+		*/
+		*sl_I64_push(&fib, perm) = a + b;
+	}
+
+	for (int i = 0; i < fib.len; i++) {
+		Buffer_appendI64(output, fib.elems[i]);
+		Buffer_appendU8(output, '\n');
+	}
+	Buffer_standardOutput(output);
+}
+
+/* These generic structures may have more than one required macro */
+#define hm_KEY_TYPE S8
+#define hm_KEY_HASHPROC S8_hash_prime19
+#define hm_KEY_EQUALSPROC S8_equal
+#define hm_VAL_TYPE U64
+#include "../hashmap.c" // will define hm_S8_U64
+
+// HASHMAPS
+FUNCTION void
+citypopulus_hashmap(Buffer *output, m_Allocator *perm)
+{
+	// We always store a hashmap pointer, NOT the actual hashmap
+	hm_S8_U64 *database = hm_EMPTY;
+
+	*hm_S8_U64_upsert(&database, S8("London"), perm) = 8800000;
+	*hm_S8_U64_upsert(&database, S8("Lahore"), perm) = 13000000;
+	*hm_S8_U64_upsert(&database, S8("Dhaka"), perm) = 21280000;
+	*hm_S8_U64_upsert(&database, S8("Washington D.C."), perm) = 679000;
+	*hm_S8_U64_upsert(&database, S8("Taxila"), perm) = 739000;
+
+	// Can't iterate through hashmap, but in exchange, accessing values is fast
+	// NOTE: passing no allocator implies that you should NOT insert a value if it doesnt exist
+	U64 dc_population = *hm_S8_U64_upsert(&database, S8("Washington D.C."), NIL);
+	U64 lahore_population = *hm_S8_U64_upsert(&database, S8("Lahore"), NIL);
+	U64 london_population = *hm_S8_U64_upsert(&database, S8("London"), NIL);
+	
+	Buffer_appendI64(output, dc_population);
+	Buffer_appendU8(output, '\n');
+	Buffer_appendI64(output, lahore_population);
+	Buffer_appendU8(output, '\n');
+	Buffer_appendI64(output, london_population);
+	Buffer_appendU8(output, '\n');
+
+	Buffer_standardOutput(output);
+}
+
+CALLBACK_EXPORT os_ErrorCode
+os_entry(void)
+{
+	m_Buddy buddy = m_Buddy_create(os_alloc(MEGA(2)), MEGA(2));
+	m_Allocator perm = m_BUDDY_ALLOCATOR(buddy);
+
+	Buffer output = BUFFER(m_MAKE(U8, KILO(2), &perm), KILO(2));
+
+	fib_slice(&output, &perm);
+	citypopulus_hashmap(&output, &perm);
+
+
+	return os_ErrorCode_success;
+}
\ No newline at end of file
diff --git a/bastd/examples/fib_slice.c b/bastd/examples/fib_slice.c
deleted file mode 100644
index cf722e9..0000000
--- a/bastd/examples/fib_slice.c
+++ /dev/null
@@ -1,59 +0,0 @@
-#define BASTD_CLI
-#include "../../bastd.c"
-
-/* The sl_TYPE macro defines the type of the generic. It is cleared after every
-   include of "../slice.c"
-*/
-#define sl_TYPE I64
-#include "../slice.c"
-
-CALLBACK_EXPORT os_ErrorCode
-os_entry(void)
-{
-	m_Buddy buddy = m_Buddy_create(os_alloc(MEGA(2)), MEGA(2));
-	m_Allocator perm = m_BUDDY_ALLOCATOR(buddy);
-
-	// Slices can be created with a backing array to start with.
-	I64 init[] = {0, 1};
-	sl_I64 fib = sl_I64_create(init, 2);
-
-	for (;;) {
-		// The data in a slice can be accessed like a normal array
-		I64 a = fib.elems[fib.len - 2];
-		I64 b = fib.elems[fib.len - 1];
-		if (a + b > 255) {
-			break;
-		}
-
-		/* The sl_TYPE_push function automatically doubles the capacity of the
-		   array if the slice is full and returns a pointer to a new element
-		*/
-		*sl_I64_push(&fib, &perm) = a + b;
-	}
-
-	Buffer output = BUFFER(m_MAKE(U8, KILO(2), &perm), KILO(2));
-	for (int i = 0; i < fib.len; i++) {
-		Buffer_appendI64(&output, fib.elems[i]);
-		Buffer_appendU8(&output, '\n');
-	}
-	Buffer_standardOutput(&output);
-
-	// Wait for you to press enter
-	Buffer_appendS8(&output, S8("I've got a message for you. Press Enter to see it: "));
-	Buffer_standardOutput(&output);
-	Buffer_appendStandardInput(&output, 1024, &perm);
-
-	sl_S8 msgs = sl_S8_create(NIL, 0);
-	*sl_S8_push(&msgs, &perm) = S8("C standard library!");
-	*sl_S8_push(&msgs, &perm) = S8("a Bravely Arranged ");
-	*sl_S8_push(&msgs, &perm) = S8("This is ");
-	*sl_S8_push(&msgs, &perm) = S8("World! ");
-	*sl_S8_push(&msgs, &perm) = S8("Hello, ");
-
-	for (; msgs.len > 0;) {
-		Buffer_appendS8(&output, sl_S8_pop(&msgs));
-	}
-	Buffer_standardOutput(&output);
-
-	return os_ErrorCode_success;
-}
\ No newline at end of file
diff --git a/bastd/hashmap.c b/bastd/hashmap.c
new file mode 100644
index 0000000..bd92886
--- /dev/null
+++ b/bastd/hashmap.c
@@ -0,0 +1,53 @@
+// GENERIC FILE, REDEFINED EVERY INCLUDE
+#ifndef hm_KEY_TYPE
+#error "No hm_KEY_TYPE given"
+#endif
+
+// hm_KEY_HASHPROC need signature "U64 procname(hm_KEY_TYPE)"
+#ifndef hm_KEY_HASHPROC
+#error "No hm_KEY_HASHPROC given"
+#endif
+
+#ifndef hm_KEY_EQUALSPROC
+#error "No hm_KEY_EQUALSPROC given"
+#endif
+
+#ifndef hm_VAL_TYPE
+#error "No hm_VAL_TYPE given"
+#endif
+
+#define hm_NAME CONCAT(CONCAT(hm_, hm_KEY_TYPE), CONCAT(_, hm_VAL_TYPE))
+
+typedef struct hm_NAME hm_NAME;
+struct hm_NAME {
+	hm_NAME *child[4];
+	hm_KEY_TYPE key;
+	hm_VAL_TYPE val;
+};
+
+// always store a pointer to the hashmap, not the actual value
+#define hm_EMPTY NIL
+
+FUNCTION hm_VAL_TYPE *
+CONCAT(hm_NAME, _upsert) (hm_NAME **m, hm_KEY_TYPE key, m_Allocator *perm)
+{
+	for (U64 h = hm_KEY_HASHPROC(key); *m; h <<= 2) {
+		if (hm_KEY_EQUALSPROC(key, (*m)->key)) {
+			return &(*m)->val;
+		}
+		m = &(*m)->child[h>>62];
+	}
+	if (perm == NIL) {
+		// just searching, dont insert a new value
+		return NIL;
+	}
+	*m = m_MAKE(hm_NAME, 1, perm);
+	(*m)->key = key;
+	return &(*m)->val;
+}
+
+#undef hm_NAME
+#undef hm_VAL_TYPE
+#undef hm_KEY_EQUALSPROC
+#undef hm_KEY_HASHPROC
+#undef hm_KEY_TYPE
\ No newline at end of file
diff --git a/bastd/memory.c b/bastd/memory.c
index eb03f2e..b05d5aa 100644
--- a/bastd/memory.c
+++ b/bastd/memory.c
@@ -352,6 +352,7 @@ m_Buddy_alloc(void *ctx, void *ptr, U64 old_size, U64 new_size) {
         if (found != NIL) {
             found->is_free = FALSE;
 			U8 *p = (U8 *)found + b->alignment;
+			m_memorySet(p, 0, new_size);
 			if (ptr != NIL) {
 				m_memoryCopy(p, ptr, old_size);
 			}
diff --git a/bastd/string.c b/bastd/string.c
index 12e2753..3eee39d 100644
--- a/bastd/string.c
+++ b/bastd/string.c
@@ -203,4 +203,16 @@ S8_join(sl_S8 s, S8 join, m_Allocator *perm) {
 	return (S8){total_length, mem};
 }
 
+// Should probably get a better hashing func, but oh well
+FUNCTION U64
+S8_hash_prime19(S8 s)
+{
+	U64 h = 0x100;
+	for (U64 i = 0; i < s.len; i++) {
+		h ^= s.raw[i];
+		h *= 1111111111111111111u;
+	}
+	return h;
+}
+
 #endif//BASTD_STRING_C
\ No newline at end of file
diff --git a/build.bat b/build.bat
index 1050e9a..a695c9d 100644
--- a/build.bat
+++ b/build.bat
@@ -7,7 +7,7 @@ set debugflags=/nologo /W3 /MTd /Od /Zi /RTC1 /fsanitize=address /link /incremen
 
 REM Uncomment one of these to run an example. Try it! They're great documentation.
 REM cl ..\bastd\examples\memory.c %debugflags%
-REM cl ..\bastd\examples\fib_slice.c %debugflags%
+REM cl ..\bastd\examples\data_structs.c %debugflags%
 REM cl ..\bastd\examples\string.c %debugflags%
 REM cl ..\bastd\examples\buffer.c %debugflags%
 REM cl ..\bastd\examples\job_random.c %debugflags%