/* Custom Properties */
:root {
  --color-bg: #050505;
  --color-text: #d4d4d4;
  --color-blood: #8a0303;
  --color-rust: #9e3d22;
  --font-en: 'Cinzel Decorative', serif;
  --font-ja: 'Noto Serif JP', serif;
}

/* Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-ja);
  line-height: 1.6;
}

a {
  color: inherit;
  text-decoration: none;
}

/* Page Layout (100vh維持) */
.page {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

.main {
  flex-grow: 1;
}

/* Header */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  padding: 1.5rem 2rem;
  z-index: 100;
  background: linear-gradient(to bottom, rgba(5, 5, 5, 0.9), transparent);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
}

.header__inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.header__spacer {
  flex: 1;
}

.header__title {
  flex: 1;
  text-align: center;
  font-family: var(--font-en);
  font-size: 2rem;
  margin: 0;
  color: var(--color-blood);
  text-shadow: 0 0 10px rgba(138, 3, 3, 0.5);
}

.header__nav {
  flex: 1;
  text-align: right;
}

.header__link {
  font-family: var(--font-en);
  font-size: 1.2rem;
  transition: color 0.3s ease;
}

.header__link:hover {
  color: var(--color-rust);
}

/* Hero Section */
.hero {
  position: relative;
  height: 100vh;
  width: 100%;
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero__canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
}

.hero__content {
  position: relative;
  z-index: 2;
}

.hero__title {
  font-family: var(--font-en);
  font-size: clamp(3rem, 8vw, 6rem);
  color: var(--color-blood);
  margin: 0;
  opacity: 0;
  /* ページ表示後、1.5秒遅延して5秒かけてじんわり表示 */
  animation: fade-in-dark 3s ease-in-out forwards;
  text-shadow: 0 0 20px rgba(138, 3, 3, 0.8), 2px 2px 0px var(--color-rust);
  letter-spacing: 0.1em;
}

@keyframes fade-in-dark {
  0% {
    opacity: 0;
    transform: scale(0.95);
    filter: blur(15px);
  }
  100% {
    opacity: 1;
    transform: scale(1);
    filter: blur(0);
  }
}

/* Concept Section */
.concept {
  padding: 8rem 2rem;
  display: flex;
  justify-content: center;
  background: radial-gradient(circle at center, #110000 0%, #050505 100%);
}

.concept__inner {
  max-width: 800px;
  text-align: center;
}

.concept__title {
  font-family: var(--font-ja);
  font-size: 2.5rem;
  color: var(--color-rust);
  margin-bottom: 2rem;
  border-bottom: 1px solid var(--color-blood);
  padding-bottom: 1rem;
  display: inline-block;
}

.concept__text {
  font-size: 1.1rem;
  line-height: 2.2;
  text-shadow: 1px 1px 3px rgba(0, 0, 0, 0.8);
}

.concept__char {
  display: inline-block;
  transform-origin: center center;
  will-change: transform, text-shadow;
}

.concept__action {
  margin-top: 4rem;
}

.concept__action-text {
  font-size: 0.9rem;
  color: #888;
  margin-bottom: 1rem;
}

.concept__button {
  display: inline-block;
  font-family: var(--font-en);
  font-size: 1.5rem;
  color: var(--color-blood);
  padding: 1rem 3rem;
  border: 1px solid var(--color-blood);
  background-color: transparent;
  transition: all 0.3s ease;
  text-transform: uppercase;
  letter-spacing: 0.2em;
}

.concept__button:hover {
  color: var(--color-bg);
  background-color: var(--color-rust);
  border-color: var(--color-rust);
  box-shadow: 0 0 15px rgba(158, 61, 34, 0.6);
}

/* Darkness Page */
.page--darkness {
  /* 血と錆が混ざり合ったような、おどろおどろしい静的なグラデーション背景 */
  background:
    radial-gradient(circle at 20% 30%, rgba(138, 3, 3, 0.15) 0%, transparent 60%),
    radial-gradient(circle at 80% 70%, rgba(158, 61, 34, 0.1) 0%, transparent 60%),
    linear-gradient(to bottom, #050505 0%, #0a0000 50%, #050505 100%);
}

.darkness-content {
  padding: 10rem 2rem 5rem;
  display: flex;
  justify-content: center;
}

.darkness-content__inner {
  max-width: 800px;
}

.darkness-content__title {
  font-family: var(--font-en);
  font-size: 3rem;
  color: var(--color-blood);
  text-align: center;
  margin-bottom: 3rem;
  text-shadow: 0 0 15px rgba(138, 3, 3, 0.5);
  letter-spacing: 0.1em;
}

.darkness-content__text p {
  margin-bottom: 2.5rem;
}

/* Footer */
.footer {
  background-color: #000;
  padding: 3rem 2rem 1rem;
  border-top: 1px solid #1a1a1a;
}

.footer__inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 2rem;
}

.footer__brand {
  font-family: var(--font-en);
  font-size: 1.5rem;
  color: var(--color-blood);
  text-shadow: 0 0 5px rgba(138, 3, 3, 0.3);
}

.footer__link {
  font-family: var(--font-en);
  font-size: 1.1rem;
  transition: color 0.3s ease;
}

.footer__link:hover {
  color: var(--color-rust);
}

.footer__copyright {
  text-align: center;
  font-size: 0.8rem;
  color: #555;
}

/* Responsive (Smartphones) */
@media (max-width: 768px) {
  .header {
    padding: 1rem;
  }
  .header__spacer {
    display: none;
  }
  .header__title {
    font-size: 1.5rem;
    flex: unset;
    text-align: left;
  }
  .header__nav {
    flex: unset;
  }
  .header__link {
    font-size: 1rem;
  }
  .hero__title {
    font-size: clamp(2.5rem, 12vw, 4rem);
  }
  .concept {
    padding: 5rem 1rem;
  }
  .concept__title {
    font-size: 2rem;
  }
  .concept__text {
    font-size: 1rem;
  }
  .concept__action {
    margin-top: 3rem;
  }
  .concept__button {
    font-size: 1.2rem;
    padding: 0.8rem 2rem;
  }
  .darkness-content {
    padding: 6rem 1rem 3rem;
  }
  .darkness-content__title {
    font-size: 2.2rem;
    margin-bottom: 2rem;
  }
  .footer {
    padding: 2rem 1rem 1rem;
  }
}