:root {
  --ice: #d4e9ff;
  --ice-bright: #eff8ff;
  --blue: #8fc7ff;
  --navy: #06122a;
  --navy-deep: #020712;
  --navy-glass: rgba(3, 8, 18, 0.68);
  --silver: #dce8f4;
  --white-soft: rgba(226, 240, 255, 0.67);
  --line: rgba(201, 227, 255, 0.2);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background: var(--navy-deep);
}

body {
  color: white;
  font-family: "Noto Sans KR", "Pretendard", "Apple SD Gothic Neo",
    "Malgun Gothic", Arial, sans-serif;
  overflow-x: hidden;
}

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

a,
button {
  -webkit-tap-highlight-color: transparent;
}

/*
  16:9 구도를 기준으로 만든 메인 화면이지만, 실제 브라우저에서는
  가로·세로 비율과 관계없이 뷰포트를 전부 채웁니다.
*/
.screen {
  position: relative;
  width: 100%;
  height: 100vh;
  height: 100svh;
  min-height: 100vh;
  min-height: 100svh;
  container-type: size;
  isolation: isolate;
  overflow: hidden;
}

.concept-three {
  color: white;
  background: var(--navy);
}

.c3-background {
  position: absolute;
  z-index: -4;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  filter: saturate(0.72) brightness(0.78) contrast(1.08);
}

.c3-gradient {
  position: absolute;
  z-index: -3;
  inset: 0;
  background:
    linear-gradient(
      90deg,
      rgba(3, 8, 20, 0.08) 0%,
      rgba(4, 10, 23, 0.15) 44%,
      rgba(2, 7, 18, 0.9) 100%
    ),
    linear-gradient(0deg, rgba(1, 5, 13, 0.72), transparent 35%);
}

.c3-grid {
  position: absolute;
  z-index: -2;
  inset: 0;
  opacity: 0.16;
  background-image:
    linear-gradient(rgba(190, 224, 255, 0.16) 1px, transparent 1px),
    linear-gradient(90deg, rgba(190, 224, 255, 0.16) 1px, transparent 1px);
  background-size: 8cqw 8cqw;
  mask-image: linear-gradient(90deg, transparent 38%, black);
  -webkit-mask-image: linear-gradient(90deg, transparent 38%, black);
}

.wordmark {
  display: grid;
  grid-template-columns: auto auto;
  align-items: center;
  column-gap: 10px;
  width: max-content;
  font-family: "Arial Black", "Noto Sans KR", sans-serif;
  font-size: clamp(22px, 1.65cqw, 34px);
  font-weight: 900;
  letter-spacing: -0.06em;
  line-height: 0.9;
}

.wordmark .mark-star {
  color: var(--blue);
  font-size: 1.15em;
}

.main-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: clamp(18px, 2.7cqw, 52px);
}

.main-nav a {
  position: relative;
  color: rgba(255, 255, 255, 0.62);
  font-size: clamp(12px, 0.78cqw, 16px);
  font-weight: 700;
  letter-spacing: 0.11em;
  transition: color 180ms ease, transform 180ms ease;
}

.main-nav a:hover,
.main-nav a.active {
  color: white;
  transform: translateY(-2px);
}

.main-nav a.active::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: -13px;
  left: 0;
  height: 2px;
  background: var(--blue);
}

.c3-header {
  position: relative;
  z-index: 8;
  display: grid;
  grid-template-columns: 0.75fr 0.7fr 2fr 0.9fr;
  align-items: center;
  height: 104px;
  padding: 0 4.3cqw;
  border-bottom: 1px solid var(--line);
  background: rgba(3, 8, 18, 0.48);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

.c3-frequency {
  color: rgba(255, 255, 255, 0.44);
  font-size: 10px;
  font-weight: 800;
  line-height: 1.5;
  letter-spacing: 0.14em;
}

.c3-frequency b {
  display: block;
  color: rgba(207, 232, 255, 0.86);
  font-size: 13px;
}

.c3-enter {
  justify-self: end;
  padding: 14px 0;
  border-bottom: 1px solid #afd6ff;
  color: #dceeff;
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0.09em;
}

.c3-sidecode {
  position: absolute;
  top: 16cqh;
  bottom: 11cqh;
  left: 2cqw;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: center;
  color: rgba(222, 239, 255, 0.48);
  font-size: 10px;
  font-weight: 800;
  letter-spacing: 0.16em;
  writing-mode: vertical-rl;
}

.c3-copy {
  position: absolute;
  z-index: 5;
  top: 15cqh;
  right: 5.5cqw;
  width: min(37cqw, 680px);
  min-width: 540px;
}

.signal {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 0 0 2cqh;
  color: #b9dcff;
  font-size: 12px;
  font-weight: 900;
  letter-spacing: 0.17em;
}

.signal i {
  display: block;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: #a4d4ff;
  box-shadow: 0 0 18px #85c8ff;
}

.c3-number {
  position: absolute;
  z-index: -1;
  top: -7cqh;
  right: -2cqw;
  color: transparent;
  font-family: "Arial Black", sans-serif;
  font-size: clamp(220px, 22cqw, 430px);
  font-weight: 900;
  line-height: 1;
  -webkit-text-stroke: 1px rgba(179, 218, 255, 0.13);
}

.c3-copy h1 {
  margin: 0;
  font-family: "Arial Black", Impact, sans-serif;
  font-size: clamp(82px, 7cqw, 136px);
  font-weight: 900;
  letter-spacing: -0.08em;
  line-height: 0.79;
}

.c3-copy h1 span {
  color: transparent;
  -webkit-text-stroke: 2px rgba(218, 237, 255, 0.88);
}

.c3-name {
  display: flex;
  align-items: baseline;
  gap: 20px;
  margin-top: 2.5cqh;
}

.c3-name b {
  font-size: clamp(30px, 2.2cqw, 43px);
  letter-spacing: -0.05em;
}

.c3-name span {
  color: #9dccfb;
  font-size: 14px;
  font-weight: 900;
  letter-spacing: 0.22em;
}

.c3-lead {
  margin: 2.5cqh 0 3cqh;
  color: var(--white-soft);
  font-size: clamp(17px, 1.06cqw, 21px);
  font-weight: 500;
  line-height: 1.75;
}

.c3-play {
  display: flex;
  align-items: center;
  gap: 16px;
  width: max-content;
}

.c3-play > span {
  display: grid;
  place-items: center;
  width: 58px;
  height: 58px;
  border: 1px solid rgba(207, 233, 255, 0.58);
  border-radius: 50%;
  color: #cae7ff;
  background: rgba(169, 213, 255, 0.08);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.c3-play p {
  margin: 0;
  font-size: 15px;
  font-weight: 900;
  letter-spacing: 0.08em;
}

.c3-play small {
  display: block;
  margin-bottom: 5px;
  color: rgba(255, 255, 255, 0.42);
  font-size: 10px;
  letter-spacing: 0.15em;
}

.c3-footer {
  position: absolute;
  z-index: 7;
  right: 0;
  bottom: 0;
  left: 0;
  display: grid;
  grid-template-columns: auto auto 1fr;
  align-items: center;
  gap: 4cqw;
  height: 84px;
  padding: 0 4.5cqw;
  border-top: 1px solid var(--line);
  background: var(--navy-glass);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
}

.c3-footer p {
  margin: 0;
  color: rgba(255, 255, 255, 0.42);
  font-size: 11px;
  font-weight: 800;
  letter-spacing: 0.12em;
}

.c3-footer b {
  color: rgba(235, 246, 255, 0.9);
}

.c3-footer .moving-line {
  justify-self: end;
  color: rgba(155, 205, 252, 0.56);
  font-family: Georgia, serif;
  font-size: 15px;
  font-style: italic;
  letter-spacing: 0.06em;
}

/* 하위 페이지 제작용 공통 템플릿 */
.template-body {
  display: block;
  min-height: 100svh;
  background:
    linear-gradient(90deg, rgba(2, 7, 18, 0.92), rgba(3, 10, 25, 0.74)),
    url("../assets/optimized/usisi-night.webp") center / cover fixed;
}

.template-header {
  position: fixed;
  z-index: 20;
  top: 0;
  right: 0;
  left: 0;
  display: grid;
  grid-template-columns: 0.8fr 2fr 0.8fr;
  align-items: center;
  height: 104px;
  padding: 0 4.3vw;
  border-bottom: 1px solid var(--line);
  background: rgba(3, 8, 18, 0.72);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
}

.template-back {
  justify-self: end;
  padding-bottom: 9px;
  border-bottom: 1px solid #afd6ff;
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0.09em;
}

.template-main {
  width: min(1180px, 88vw);
  margin: 0 auto;
  padding: 170px 0 90px;
}

.template-kicker {
  margin: 0 0 16px;
  color: rgba(188, 221, 253, 0.45);
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0.2em;
}

.template-main > h1 {
  margin: 0;
  color: transparent;
  font-family: "Arial Black", Impact, sans-serif;
  font-size: clamp(72px, 9vw, 160px);
  line-height: 0.9;
  letter-spacing: -0.07em;
  -webkit-text-stroke: 2px rgba(221, 239, 255, 0.9);
}

.template-description {
  max-width: 720px;
  margin: 34px 0 54px;
  color: rgba(226, 240, 255, 0.7);
  font-size: 18px;
  line-height: 1.8;
}

.template-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 22px;
}

.template-grid article {
  min-height: 240px;
  padding: 38px;
  border: 1px solid rgba(205, 230, 255, 0.22);
  background: rgba(5, 14, 29, 0.58);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

.template-grid small {
  color: #9dccfb;
  font-size: 11px;
  font-weight: 900;
  letter-spacing: 0.16em;
}

.template-grid h2 {
  margin: 24px 0 14px;
  font-size: 28px;
}

.template-grid p {
  margin: 0;
  color: rgba(226, 240, 255, 0.58);
  font-size: 16px;
  line-height: 1.7;
}

@media (max-width: 1180px) {
  .c3-header {
    grid-template-columns: 0.7fr 0.6fr 1.7fr 0.8fr;
  }

  .c3-copy {
    right: 4cqw;
    min-width: 460px;
  }

  .main-nav {
    gap: 18px;
  }

  .main-nav a {
    font-size: 11px;
  }
}

@media (max-width: 820px) {
  body {
    display: block;
  }

  .screen {
    width: 100%;
    height: max(820px, 100svh);
    min-height: max(820px, 100svh);
    container-type: size;
  }

  .main-nav,
  .c3-frequency,
  .c3-enter,
  .c3-sidecode {
    display: none;
  }

  .c3-header {
    grid-template-columns: 1fr;
    height: 76px;
    padding: 0 22px;
  }

  .c3-background {
    object-position: 35% center;
  }

  .c3-gradient {
    background: linear-gradient(
      0deg,
      rgba(1, 5, 13, 0.96),
      rgba(2, 8, 20, 0.12) 80%
    );
  }

  .c3-copy {
    top: auto;
    right: 22px;
    bottom: 112px;
    left: 22px;
    width: auto;
    min-width: 0;
  }

  .c3-copy h1 {
    font-size: 74px;
  }

  .c3-number {
    top: -70px;
    right: 0;
    font-size: 220px;
  }

  .c3-footer {
    grid-template-columns: 1fr;
    height: 72px;
    padding: 0 22px;
  }

  .c3-footer p:not(:first-child) {
    display: none;
  }

  .template-header {
    grid-template-columns: 1fr auto;
    height: 76px;
    padding: 0 22px;
  }

  .template-main {
    width: min(90vw, 680px);
    padding-top: 130px;
  }

  .template-grid {
    grid-template-columns: 1fr;
  }
}

@media (prefers-reduced-motion: no-preference) {
  .signal i {
    animation: signal-pulse 1.8s ease-in-out infinite;
  }
}

@keyframes signal-pulse {
  0%,
  100% {
    opacity: 0.65;
  }
  50% {
    opacity: 1;
    box-shadow: 0 0 24px #85c8ff;
  }
}