According to https://en.wikipedia.org/wiki/Atari_8-bit_computer_peripherals it seems appropriate to add a JOY_FIRE definition for the ATARI.
#define JOY_RIGHT_MASK 0x08
#define JOY_BTN_1_MASK 0x10
+#define JOY_FIRE_MASK JOY_BTN_1_MASK
+#define JOY_FIRE(v) ((v) & JOY_FIRE_MASK)
+
/* color register functions */
extern void __fastcall__ _setcolor (unsigned char color_reg, unsigned char hue, unsigned char luminace);
extern void __fastcall__ _setcolor_low (unsigned char color_reg, unsigned char color_value);