Huygens Principle

Huygens Principle is a top-down shooter where the player’s main character possesses the unique power to become the person they have just killed. Driven by a desire for revenge, the protagonist embarks on a journey through space, time, and hell. The game features fast-paced, hardcore gameplay that requires not only sharp shooting skills but also strategic decision-making at every moment, as players must constantly choose their next form. It includes 169 levels across 13 chapters, each set in a unique location, and is accompanied by a retro/synthwave soundtrack.

Huygens Principle: A Forgotten Gem of Mechanically-Driven Revenge

In the vast, churning ocean of indie games released each year, countless titles vanish into the abyss, remembered only by their developers and a handful of dedicated players. Huygens Principle, a 2017 top-down shooter from the enigmatic Cat in Jar Games, is one such title—a game that, despite its obscurity and rough-hewn presentation, possesses a singular, brilliant mechanical hook that elevates it from being a mere Hotline Miami homage to a unique and challenging experience worthy of excavation. This review aims to provide that long-overdue critical examination, arguing that while the game is undeniably flawed in its narrative and aesthetic execution, its innovative core gameplay loop and sheer, unadulterated challenge cement its place as a fascinating, if deeply niche, footnote in the history of indie action games.

Development History & Context

A Jar of Ambition: The Studio Behind the Curtain

The development story of Huygens Principle is as opaque as its plot. The game was developed by the mysteriously named Cat in Jar Games and published by Dagestan Technology, entities about which little is known and even less is documented. This anonymity is a hallmark of many small-scale indie projects from the late 2010s, often developed by individuals or tiny teams operating with minimal budgets and even less publicity. The game was built using the Cocos2d-x engine, a free, open-source framework popular for 2D mobile and desktop games. This technological choice is telling; it points to a development priority focused on functionality and accessibility over graphical fidelity or cutting-edge tech.

Released on September 15, 2017, for Windows via Steam, Huygens Principle entered a marketplace still deeply under the influence of Dennaton Games’ seminal Hotline Miami (2012). The top-down, ultra-violent, synthwave-drenched shooter had become a genre unto itself, with countless indie developers attempting to capture its lightning-in-a-bottle mix of style, speed, and punishment. For Cat in Jar Games, the goal was not to merely replicate but to iterate—to take that established formula and inject it with a new, defining mechanic that would set their project apart in a crowded field.

Narrative & Thematic Deep Dive

A Thin Veil for a Mechanic: Revenge Across Time and Space

If Huygens Principle has a primary weakness, it is its narrative and world-building. The official description provides the entire setup: the main hero possesses a unique power—upon killing someone, he immediately inhabits their body. His sole motivation is revenge. To achieve this, he journeys “through space, time and hell.”

This is the extent of the narrative scaffolding. There are no cutscenes, no character development, no dialogue, and no explanation for why the protagonist seeks revenge, who wronged him, or the logic connecting a medieval crusade to a cyberpunk future to a police station raid. As one player review on RAWG astutely noted, there is “no coherence between the worlds.” The levels are simply a series of 13 disconnected chapters (totaling 169 levels) that serve as themed arenas for the gameplay.

Thematically, the game touches on concepts of identity, continuity of consciousness, and the cost of vengeance. The core mechanic forces the player to literally become the very thing they destroy, a provocative idea that remains frustratingly unexplored. The title itself, “Huygens Principle,” is a physics concept related to wave propagation, which feels like an intellectual reach for a game that does not engage with its own premise on a deeper level. The narrative exists solely to facilitate the mechanic; it is a premise, not a story. For players seeking a rich, thematic experience, Huygens Principle will be a profound disappointment. Its ambitions lie elsewhere.

Gameplay Mechanics & Systems

The Brilliant Core: “You Are What You Kill”

This is where Huygens Principle transforms from a forgetgettable clone into a compelling, challenging, and genuinely innovative experience. The entire game is built around one brilliant mechanic: when you kill an enemy, you instantly possess their body and their weapon.

This is not a simple weapon swap. It is a fundamental shift in the gameplay loop that introduces layers of strategic decision-making:
* Tactical Positioning: Every kill is a teleport. You must plan your chain of kills not just to eliminate threats, but to reposition yourself advantageously across the battlefield. A missed shot could leave you possessing a body surrounded by enemies, leading to instant death.
* Resource Management: Weapons are limited to the ammunition in the clip of the enemy you kill. You cannot reload. This forces a constant, aggressive forward momentum. You must keep killing to keep a viable weapon, making ammo conservation a critical, moment-to-moment calculation.
* Identity as Tool: Your “character” is transient. You are a consciousness hopping between vessels. This mechanically reinforces the thematic notion of a fractured identity consumed by a singular goal.

The game expertly builds upon this foundation with variant chapters that alter the rules:
* A SUPERHOT Homage: One chapter adopts the mechanic where “time moves only when you move,” forcing players to think in frozen, tactical increments.
* No-Power Chapters: Sections where the possession mechanic is disabled, challenging the player to rely on pure shooting skills and environmental awareness.
* Slow-Mo Segments: Areas that introduce bullet time, allowing for more precise planning amidst the chaos.

The gameplay is described accurately by players as “fast-paced and hardcore.” It is brutally difficult, demanding pixel-perfect precision, lightning-fast reflexes, and strategic foresight. The UI is minimal and functional, and the controls (keyboard and mouse) are direct and responsive, which is essential for a game of this speed. The “gamefeel” is crunchy and impactful; kills are satisfyingly immediate. While the mechanic is superb, its execution can sometimes feel janky—the instant transition can be disorienting, and the difficulty curve is steep and occasionally unfair. Yet, these flaws are part of its raw, unfiltered charm.

World-Building, Art & Sound

Aesthetic Dissonance: Where the Game Stumbles

The visual presentation of Huygens Principle is its most criticized aspect. The art is minimalist to a fault, appearing more like a functional prototype or placeholder than a finished product. The environments are simple, flat-colored geometric shapes. Character sprites are small and lack detail. There is no animation to speak of beyond basic movement and the muzzle flash of guns. One reviewer on RAWG perfectly captured the sentiment: “It Looks like a playholder of the future project… Why is it so tasteless to spoil a wonderful idea?”

However, the sound design is where the game finds its soul and redeems its visual shortcomings entirely. The soundtrack is a powerhouse retrowave/synthwave score featuring 16 tracks from artists like ALEX, CYBERCORPSE, Dupre, EMMETT BROWN, Reno, and Wice. This music is not merely background noise; it is the engine of the experience. The pulsing, energetic beats perfectly complement the high-speed, high-stakes gameplay, driving the player forward and elevating the action. The sound effects—the crack of a pistol, the blast of a shotgun, the digital zip of a body transfer—are crisp and effective, providing essential audio feedback in the visually sparse world. The art fails to impress, but the sound absolutely succeeds in creating a specific, intense atmosphere.

Reception & Legacy

A Cult in Waiting: Obscurity and Acclaim

Upon its release, Huygens Principle made almost no critical splash. There are no professional critic reviews on Metacritic or MobyGames. Its commercial performance appears to have been minimal. For all intents and purposes, it was lost to time upon arrival.

However, the small cohort of players who discovered it recognized its qualities. On Steam, it holds a “Positive” rating with a Player Score of 93/100 (based on 15 reviews as of 2025). The reviews that exist are effusive in their praise for its core innovation. Players call it an “excellent little retro game” and a “wonderful chellendzhevym test,” consistently highlighting the possession mechanic as a genius twist on a familiar formula.

Its legacy is one of a hidden gem, a game studied by aficionados of indie design for its bold, single-minded focus on one great idea. While it did not influence the industry on a macro scale, it stands as a testament to the ethos of indie development: that a game can be built around one powerful mechanic and can find an audience, however small, that appreciates it for precisely that. It is a direct descendant of Hotline Miami‘s design philosophy and a contemporary that dared to ask, “What if we changed the fundamental rule of engagement?”

Conclusion

Huygens Principle is a game of stark contrasts. It is a title with a narrative that is practically non-existent and visuals that are unabashedly rudimentary. Yet, it is also a game with a gameplay mechanic so innovative and well-executed that it carries the entire experience on its back. It is a challenging, frustrating, and ultimately rewarding exercise in pure action-game design.

Its place in video game history is not in the mainstream but in the margins—a cult classic for a cult that never quite formed. It is a fascinating case study for how a brilliant central idea can elevate a project, and how a lack of polish in other areas can prevent that idea from reaching the audience it deserves. For students of game design and hardcore fans of the genre willing to look past its glaring flaws, Huygens Principle is a forgotten puzzle piece worth finding. It is not a masterpiece, but it is, unequivocally, a principle worth experiencing.