* Secret characters : when the 'Game Over' screen appears, hold the UP key until the screen changes. The bear (kuma) and the valley (tani) should appear on the title screen. It means that this game has been developed by Taito Kumagaya (kuma + tani) Laboratory. And if you start the game when these characters are displayed, one life is added to your play (3 by default, so the game should start with 4 lives).
* Wave a flag at a lamp post with a red orb inside it and you will get a powerup.
* There are several types of letters or messages :
White - increase range
Red - increase firepower
Yellow - big letters
* You can also pick up 'eggs' along the way. These eggs are activated by hitting fire & flag at the same time.
Blue - freezes all monsters for a given period of time, also those off screen.
Yellow - kill everything on screen.
* The 'gremlins' don't kill you but they slow you down. You can lose them by running around a lamppost.