Imperishable Night

Imperishable Night utilises a 'time' counter, which requires the player to collect a certain amount of "time points", which are acquired in the same manner as regular points – collecting point items, grazing enemy bullets, or killing enemies. The game begins at 11:00 PM, and with each stage, thirty minutes passes, or an hour if they fail to gather enough time points. The player will receive a bad ending if the clock reaches 5:00 AM. Time will also advance by half an hour if the player uses a continue, or fails any of the Last Spells of Kaguya Houraisan, the game's final boss, who is also the only character to have multiple Last Spells. Because of this system, Imperishable Night is the only Touhou game in which the player can use a continue, and still get the good ending.

Imperishable Night features a total of eight playable characters, in pre-set pairs, and, upon completing the game with all teams, the game allows the player to select these characters individually. Each pair consist of one human, and yōkai, with the human being the player's unfocused shot, and the yokai as the focused shot.

A gauge on the lower left corner of the screen keeps track of how human or yōkai the player is, and affects the player's score accordingly. The gauge, ranging from -100% (human) to 100% (yōkai), is determined by which mode the player uses more. When the player reaches 80%, they can collect time orbs by hitting enemies (as a human) or by grazing against bosses and killing enemies (as a yōkai). Because Youmu Konpaku of the Netherworld Dwellers team is a half-ghost, their gauges are adjusted accordingly (-50% to 50% solo, -50% to 100% as the team), and the minimum values for time orb collection are reduced.

Some enemies use familiars that change their vulnerabilities depending on whether the player is playing as a human or a yōkai at the moment. These familiars are completely invulnerable when the player switches to a yōkai, but at the same time these familiars cannot collide with the yōkai player and do not shoot bullets when the player is on top of them. The enemies' alternating vulnerabilities in this game have been compared to Ikaruga.[1] Bosses may also change their standard attacks depending on the orientation of the player, usually firing slower bullets and/or homing bullets when the player is a yōkai.

Eirin Yagokoro's "Last Word" in Spell Practice Mode

The Spell Practice Mode is unlocked by beating the game with the normal ending (i.e. before the game time reaches 5:00 am). This feature allows a character/team to practice any of the game's spell cards, so long as they have encountered them. In this mode, players have only one life and cannot use their spell cards. Clearing spell cards here will show the creator's own comments on the spell cards or the characters associated with them. The stage practice, introduced in Embodiment of Scarlet Devil, allowing the player to practice an entire stage, provided they have completed it already, is also present in Imperishable Night.

Only available in the Spell Practice Mode are Last Words, which are typically the hardest spell cards in the game. These spells are earned by accomplishing certain feats such as beating the game using certain characters, or capturing a large enough number of spell cards.

Initially, the player must play with one of the four preset teams. After the player has beaten Kaguya with all four teams, then it is possible to play the characters individually. Playing as individuals instead of teams does not change the story.

• Illusionary Border Team (幻想の結界チーム) — Ever since the moon got replaced with a fake one, Yukari hasn't been able to sleep. Because Yukari doesn't go out much, she had to rope Reimu in as a guide.
  • Reimu Hakurei (博麗 霊夢 Hakurei Reimu) — Attacks using homing amulets.
  • Yukari Yakumo (八雲 紫 Yakumo Yukari) — The yōkai who controls boundaries. Attacks using needles and her shikigami Ran, who targets and attacks onto enemies.
• Aria of Forbidden Magic Team (禁呪の詠唱チーム) — Annoyed at how the humans are oblivious to what's going on, Alice tried to solve the mystery by herself, but she ended up bribing Marisa with books to make her tag along.
  • Marisa Kirisame (霧雨 魔理沙 Kirisame Marisa) — A witch who lives in the Forest of Magic. Attacks using magic missiles.
  • Alice Margatroid (アリス・マーガトロイド) — Marisa's fellow magician who also lives in the Forest of Magic. Attacks with her doll, Shanghai, who fires a laser.
• Visionary Scarlet Devil Team (夢幻の紅魔チーム) — Remilia sent Sakuya to investigate, but she failed to notice anything wrong. Remilia then went out to deal with the incident herself, with Sakuya following behind.
  • Sakuya Izayoi (十六夜 咲夜 Izayoi Sakuya) — The maid of the Scarlet Devil Mansion. Throws her knives over a wide area.
  • Remilia Scarlet (レミリア・スカーレット) — Mistress of the Scarlet Devil Mansion. Can station her shots in one place while she moves elsewhere.
• Netherworld Dwellers' Team (幽冥の住人チーム) — Yuyuko and Youmu both sensed something was wrong from the Netherworld, but Yuyuko wasn't too confident in Youmu to let her investigate by herself, since someone who could manage to seal the real moon away must be very powerful, so both Yuyuko and Youmu set out.
  • Youmu Konpaku (魂魄 妖夢 Konpaku Youmu) — Half-human half-ghost gardener of the Netherworld. Fires with her ghostly half, which acts as an option that fires opposite to her move direction.
  • Yuyuko Saigyouji (西行寺 幽々子 Saigyouji Yuyuko) — Ghostly princess of the Netherworld. Attacks with ghost familiars with wide shots.

• Wriggle Nightbug (リグル・ナイトバグ) — Stage one mid-boss and boss, a firefly youkai who happens to be in the way.
• Mystia Lorelei (ミスティア・ローレライ) — Stage two mid-boss and boss, a night sparrow preying on humans.
• Keine Kamishirasawa (上白沢 慧音 Kamishirasawa Keine) — Stage three mid-boss, boss, and Extra stage midboss. A teacher of the terakoya in the Human Village who turns into a hakutaku during full moons. Keine returns as the midboss of the extra stage in her hakutaku form.
• Reimu Hakurei — Stage four boss when playing as Marisa/Alice or Sakuya/Remilia. Reimu is looking for the one who stopped the passage of time.
• Marisa Kirisame — Stage four boss when playing as Reimu/Yukari or Youmu/Yuyuko. Like Reimu, Marisa is searching for whoever she thinks is the one lengthening the night.
• Tewi Inaba (因幡 てゐ Inaba Tewi) — Stage five midboss, a youkai rabbit based on the "White Hare of Inaba" story who has taken residence in Eientei. She is the leader of the earthly bunnies of the Eientei. Despite her deceitful personality, she is also considered a bringer of luck.
• Reisen Udongein Inaba (鈴仙・優曇華院・イナバ) — Stage five boss, a moon rabbit who deserted from the Moon when it was at war with Earth, now a disciple of Eirin. She has the power to drive people mad with her eyes — mainly in the form of hallucinations — as well as communicate telepathically with her kind. She also has control over waves of all kinds, such as light waves, brainwaves, electromagnetic waves, as well as sound waves.
• Eirin Yagokoro (八意 永琳 Yagokoro Eirin) — Stage six midboss and boss of path A and stage 6 midboss of path B. A master pharmacist who, long ago, produced the elixir of life for Kaguya, causing Kaguya to be exiled from the moon. She is the brains of Eientei. Based on the Shinto deity Omoikane.
• Kaguya Houraisan (蓬莱山 輝夜 Houraisan Kaguya) — Stage 6 boss of path B. Her character is based on Kaguya-hime from Tale of the Bamboo Cutter (also known as Tale of the Princess Kaguya), who was originally from the moon but now lives as a commoner in Gensokyo, hiding from the Lunar emissaries who want her back.
• Fujiwara no Mokou (藤原 妹紅) — Extra stage boss, a girl who, by some chance, swallowed the elixir of life and became immortal. She held a millennium-long grudge against Kaguya for humiliating her father when he was seeking Kaguya's hand in marriage. Unable to die by any means, she and Kaguya attack each other and reincarnate on a daily basis.