Ikaruga is my nemesis. It's a lean vertical shooter that can technically be completed in a half-hour run. There are no weapon upgrades, there's no ship customisation, there are no mission briefings. You're a lone freedom fighter on a quest to destroy the battle machines of the oppressive Horai army. You have only two lives to survive five levels of cruel bullet-hell perfection. The rules are simple. Enemies, and the projectiles they fire, come in light and dark forms. You can switch the polarity of your ship between light and dark states at any time, absorbing bullets of the same colour to power your homing missile attack. Take a hit from a bullet of opposite polarity and you're dead. Enemies fall to light and dark bullets, but take double damage from bullets of opposite polarity.