Ibara

Ibara is a vertical scrolling shooter developed by Japanese developer Cave and published by Taito. Although interest among the hardcore audience is high, it has currently not been published outside of Japan due to the genre's dwindling popularity in North America and arcade gaming in general.

Ibara is very similar to 8ing/Raizing's Battle Garegga and Battle Bakraid games (in fact, Shinobu Yagawa, the programmer for the aforementioned games, worked on this game). So much so that Ibara could be considered a pseudo-sequel or, at least, a spiritual successor. The similarities are numerous - some are subtle, some are easily spotted. These include combining archaic technology such as biplanes with more advanced machinery; firing and power-up system; and a medal collecting system which drastically increases scoring. The game features a similar method of earning bombs and a delay when launching them as well. Some of the enemies and their attack patterns are very familiar such as the large cranes in stage 1 and the minigun-wielding first boss. The enemy's explosions spiral around when destroying some of the heavier weapons/scenery and thin, seemingly camouflaged enemy bullets are scattered around the play area in comparable patterns. More subtle references include the HUD layout which lists the name of the current stage at the top of the screen and, when starting a stage, tells users the title of the background music that is playing.

A notable feature of Ibara is the inclusion of a variable, real-time difficulty system by way of the Rank system. The player's rank increases as they acquire more items and cause more damage, increasing the difficulty of the game along with it. The number of enemies doesn't increase but the number of bullets fired towards the user does, often reaching a ridiculous level of bullet density. There are ways of lowering this rank system if the odds appear too much. The only known way of decreasing your Rank in Ibara is to die. The more lives you have, the less the rank decreases when you die. In the later version, Ibara Kuro: Black Label, Rank can be decreased by cancelling bullets with a bomb, however Rank also increases much faster in this version, potentially increasing from minimum to maximum in a matter of seconds.

Source: Wikipedia, "Ibara (video game)", available under the CC-BY-SA License.