diff --git a/engine/slc.h b/engine/slc.h
index 99a7264..d498493 100644
--- a/engine/slc.h
+++ b/engine/slc.h
@@ -1,15 +1,81 @@
 #ifndef SLC_H
 #define SLC_H
 
-/** A word starts right after this - a word is usually after this memory area */
+/** Possible word types */
+enum SLC_WORDTYP {
+	/** Still in plain text */
+	SLC_WORDTYP_TEXT = 0,
+	/** Native code, use get_word_storage_offset to get what to run (relative pointer or array of pointers) */
+	SLC_WORDTYP_NATIVE = 1,
+	/** "Threaded code" (utf16-like word offsets) and encoded parentheses IN-PLACE inlined where text was before */
+	SLC_WORDTYP_THREADED_INLINE = 2,
+	/** "Threaded code" that did not fit in-place and is thus stored in session storage, word offset tells where */
+	SLC_WORDTYP_THREADED_SESSION = 2
+};
+typedef enum SLC_WORDTYP SLC_WORDTYP;
+
+/** Gets the wordtyp from a flags field - see wordstart */
+static inline SLC_WORDTYP get_word_type(uint8_t flags) {
+	return (SLC_WORDTYP)(flags >> 6);
+}
+
+/** Gets the 6-bit variable count (at most 64 vars possible per word) */
+static inline uint8_t get_word_var_count(uint8_t flags) {
+	return (flags && 0x3F); /* 0011 1111 */
+}
+
+/** Gets the 24bit storage offset of the word: Natives contain pointers in an offseted array */
+static inline uint32_t get_word_storage_offset(uint8_t high_offset, uint16_t low_offset) {
+	return ((uint32_t)high_offset << 16) + low_offset;
+}
+
+/**
+ * A word definition starts right after this. After processing it, we inline overwrite random parts of it in memory...
+ *
+ * Examples:
+ *
+ * 	#: just_code
+ * 	  #dup
+ * 	  #inc
+ * 	  #swap
+ * 	#
+ *
+ * 	: with_vars @a; @b; @c;
+ * 		@a
+ * 		inc
+ * 		@a(.)
+ * 	;
+ *
+ * 	#builtin: to_prefix
+ * 		#swap
+ * 		#dup
+ *
+ * TODO: How to do this builtin to be properly changed inline? If it can be inline threaded-coded, then its fine, but is spec-case
+ * 	^^The above always needs starting '#builtin' at the definition and inside. That is exchanged to real prefix...
+ *    This is used for implementation implementing built-ins with FORTH-like code instead of native (saves native interpret. space)
+ *
+ * 	#: structural (
+ * 		#parse_num
+ * 		#dup
+ * 		#inc
+ * 		#swap
+ * 		#print
+ * 		#print
+ * 	) [ #parse_num #print ] { #parse_num #print }
+ * 	#
+ */
 struct wordstart {
-	/* : */
-	char colon;
-	/* whitespace after ':', usually used to store the flags */
+	/** The ':' char - after processing it stores the flags */
 	uint8_t flags;
-	/* char name[]; // The name of the word being defined. */
-	/* char vars[]; // The local variables of the word. */
-	/* char data[]; // The "body" of the word - either text source or after processing the threaded code of it (see flags) */
+	/** whitespace after ':' and first char of name - after processing contains the high-offset */
+	uint16_t high_offset;
+	/** Either remaining parts of the name - or the leading tab/space for starting variables (or newline if there's none) */
+	uint8_t low_offset;
+	/* char ..name[]; // The REMAINS of name of the word being defined. Can be empty! */
+	/* char vars[]; // The local (at least 1-letter) variables of the word. Can be empty - min 4x8bit per a var, like: " @a;" */
+	/* char newline; // there is always a newline at this point! XXX: "@a; ", "@b;\n" is how we store vars (*/
+	/* char data[]; // The "body" of the word - either text source or inline threaded code (at least 1 character) */
+	/* char ender[]; // The ender-string that ends the word - always at least 1 character! */
 };
 typedef struct wordstart wordstart;
 
@@ -128,8 +194,11 @@ typedef uint32_t (*coderead)(SLC_CODE_OP op, uint32_t i);
  * @param insert_stack Used for temporarily expanding the input stream (one word level above) with words
  * @param session_storage Can allocate and use arbitrary memory with this.
  * @param io_connector The engine uses this to open/close pipes/files and write/read them.
+ * @param prefix The prefix added to the lookup of built-ins.
+ * @param ender The character string that ends a word definition.
+ * @param varprefix The character string that prefixes variable declarations.
  */
-void slc(
+static inline void slc(
 	coderead code_src,
 	sym symbol_table,
 	stack code_stack,