+void obfuscate_bitmap(unsigned char *bmp, int bits, int decode);
+
+/* allocates output each time. len is always in bytes of binary data.
+ * May assert (or just go wrong) if lengths are unchecked. */
+char *bin2hex(const unsigned char *in, int inlen);
+unsigned char *hex2bin(const char *in, int outlen);
+
+/* Sets (and possibly dims) background from frontend default colour,
+ * and auto-generates highlight and lowlight colours too. */
+void game_mkhighlight(frontend *fe, float *ret,
+ int background, int highlight, int lowlight);
+
+/* Randomly shuffles an array of items. */
+void shuffle(void *array, int nelts, int eltsize, random_state *rs);
+
+/* Draw a rectangle outline, using the frontend's draw_line. */
+void draw_rect_outline(frontend *fe, int x, int y, int w, int h,
+ int colour);