These days the term 'bullet hell' gets thrown around a little too enthusiastically, and not only in the 2D shooter space.
Thanks to the genre's now entrenched renaissance, the label has transcended its former status as part of the lexicon of a niche online community, evolving into part of the everyday language of gaming more broadly. And so it is that marketers today eagerly pack press releases with claims that a new FPS or roguelike action-RPG brings 'bullet hell' delights.
In truth, 'bullet hell' describes a very specific type of shooter, where overwhelmingly dense curtains of enemy firepower, diminutive hitboxes, aggressive difficulty, cavernous scoring complexity and frenetic pacing are all present. Others might tell you that a certain visual style defined by ornate pixel-based sprite work and gaudy firepower are equally defining.