diff --git a/src/lstd.c b/src/lstd.c
deleted file mode 100644
index 71765ad..0000000
--- a/src/lstd.c
+++ /dev/null
@@ -1,56 +0,0 @@
-/**
- * @file lstd.c
- *
- * @brief Portable replacements for some functions.
- */
-#include "lstd.h"
-
-#define lstd_checkascii(k)  ((k & 0xff) == k) /**< Check to see if k is in ascii area. */
-
-/**
- * @brief Check to see if a key is alpha.
- *    @param k Key to check.
- *    @return 1 if is alpha.
- */
-int lstd_isalpha(SDLKey k) {
-  int ret;
-
-  ret = 0;
-
-  /* Alpha. */
-  if((k >= SDLK_a) && (k <= SDLK_z))
-    ret = 1;
-
-  return ret;
-}
-
-/**
- * @brief Check to see if a key is alphanumeric.
- *    @param k Key to check.
- *    @return 1 if is alphanumeric.
- */
-int lstd_isalnum(SDLKey k) {
-  int ret;
-
-  ret = 0;
-
-  /* Alpha. */
-  if((k >= SDLK_a) && (k <= SDLK_z))
-    ret = 1;
-
-  /* Number. */
-  if((k >= SDLK_0) && (k <= SDLK_9))
-    ret = 1;
-
-  return ret;
-}
-
-/**
- * @brief Check to see if a key is a control character.
- *    @param k Key to check.
- *    @param 1 if is a control character.
- */
-int lstd_iscntrl(SDLKey k) {
-  return lstd_checkascii(k) ? iscntrl(k) : 0;
-}
-
diff --git a/src/lstd.h b/src/lstd.h
index 0990aa9..f4b512c 100644
--- a/src/lstd.h
+++ b/src/lstd.h
@@ -1,7 +1,23 @@
 #pragma once
-#include <SDL/SDL.h>
+#include <ctype.h>
 
-int lstd_isalpha(SDLKey k);
-int lstd_isalnum(SDLKey k);
-int lstd_iscntrl(SDLKey k);
+/**
+ * @brief Check to see if k is in ascii area.
+ */
+#define lstd_checkascii(k) ((k & 0xff) == k)
+
+/**
+ * @brief Check see if a key is alpha.
+ */
+#define lstd_isalpha(k) (lstd_checkascii(k) ? isalpha(k) : 0)
+
+/**
+ * @brief Check see if a key is alphanumeric.
+ */
+#define lstd_isalnum(k) (lstd_checkascii(k) ? isalnum(k) : 0)
+
+/**
+ * @brief Check see if a key is a control character.
+ */
+#define lstd_iscntrl(k) (lstd_checkascii(k) ? iscntrl(k) : 0)