When a boss approaches a warning blares at you from the centre of the screen - "NO REFUGE". The message became etched in my mind as I retried each level. Ikaruga is authoritarian. There's little room to explore different playstyles or approaches. You have to parse the entwined patterns of fire to find tiny pockets of survivability, and then snake through with pixel-perfect precision. The momentary pause as your ship boosts between sections is the only breathing room you have.
Every polarity flip requires a mental shift. Deadly spaces are suddenly safe. One button press changes the meaning of the entire space, and you'll need to switch constantly to survive. In its most difficult moments, Ikaruga demands an almost trance-like level of total concentration. It's almost perfect, only occasionally over-reliant on rote learning. The wall of lasers that blasts laterally across act three's speedy tunnel is near-impossible to avoid without foreknowledge, for example. The boss that crashes upwards from the bottom of the screen a little later will put a cheap end to many.
It's hard. Probably the hardest game I've ever played. But Ikaruga rewards obsession with an extraordinary sense of achievement, and hides deeper challenge within its violent match-three metagame. To increase your score multiplier, you must kill enemies in sequences of three of the same affinity. Kill two light enemies and then a dark enemy, for example, and the chain is broken.
This changes everything. Suddenly it's clear that those detailed enemy manoeuvres are carefully designed duck shoots, inviting you to complete dextrous triple-kills to keep the chain alive. Then you notice that that obliterating waves efficiently unlocks extra mini-waves - more fodder for the ever-growing chain multiplier. Keep playing past completion, and Ikaruga transforms from a survival game to a puzzle game that unfolds at the limits of human reaction speed.
Stringing chains together is the only way to break the upper echelons of Ikaruga's global score boards. Originally an arcade game, Ikaruga saw release on the Dreamcast and the Gamecube prior to this, but the PC port is excellent. You can seamlessly upload videos of your runs to the scoreboard, and download others' to watch. The framerate only falters from 60fps when bosses explode - slowdown that's present in every version of Ikaruga. If you have a widescreen monitor that rotates I'd hugely recommend swivelling it to portrait position and switching to vertical mode in the options menu. It looks stunning. It is surprisingly playable with a mouse and keyboard, but a controller is recommended. There is local co-op support, but sadly none for online multiplayer.
That's a minor quibble, though. If you love challenge at its most agonising and cathartic, Ikaruga is a worthy and maddening obsession. Splash the £7 / $10 asking price, and prepare to embrace your new gaming nemesis. I did, and after many hours with several versions of the game, I can only echo the main character's mistranslated motto: "I am not regret".