This updated version was released exactly one year after the original game’s debut. 1943 Kai is an enhanced, “wild” version of 1943 that was made only available in Japan under the name 1943 Kai: Midway Kaisen (or 1943?: ????????). Most of the graphics and sounds have been reworked, the weapons have been made more extreme and some fairly strange things (laser-firing WWII planes and ships that run on ground) have been added. The trademark P-38 has been replaced with a biplane Boeing Stearman E75 N68828. This version contains many additional levels and original music.
A little known trick in the game is to hold down the fire A button at the very end of a board immediately after beating the boss. By holding down the button until the plane takes off in the subsequent board, the game gives you a full ammunition load 65 Seconds. This trick only works every third board or so and it may even change your selected weapon. In each boss level, kill all the enemies except the boss. If you do not kill the boss you will start back at the beginning of the level. This trick works only one time for each level boss, but in the last level, round 16, if you never kill the boss you will continue to start back at the beginning every time. It is theoretically possible to score an infinite amount of points.
Pressing both buttons simultaneously causes the player’s ship to loop out of the 2-D action plane temporarily. This is very useful for getting behind enemy planes. Pressing Special calls up a special attack lightning in the air, a wave over water, but also uses up the player’s energy. The game is over when the player runs out of energy, but energy can be replenished via power-ups or for completing a level. Likewise, in two-player mode, players can share life energy by placing both planes over each other for two seconds.