>>17
>when deciding to use kanji or hiragana, i thought it was chosen baised on target audience
This is one of general rules so has exceptions. Using kanji can also add intelligence, manliness or other characteristics, depending on words.
As for the example, the game title conveys an aggressive spirit and manliness in a funny or exaggerated way. But ひとり can be in hiragana without losing much aggressiveness. I may be totally wrong, but maybe that's because ひとり is a common 訓読み word (this usually means not-Chinese-imported), and has the neutral meaning.
燃えろ and 闘え also are 訓読み words but they have aggressive meanings so they fit better in kanji, especially in the game title. Conversely, 応援 (ou-en) is an 音読み word and has a kanji-sh meaning, so only games for kids or loli-featured hentai would write it in hiragana.