:root {
  --hero-height: 100vh;
  --bg-image: url("city-bg.jpg");
  --bg-shift-distance: 20px;
  --bg-duration-slow: 18s;
  --bg-duration-fast: 4s;
  --logo-width: 47%;
  --logo-top: 18%;
  --logo-left: 53%;
  --flash-width: 420px;
  --flash-left: 15%;
  --flash-bottom: 15%;
  --flash-center-width: 380px;
  --about-width: 30%;
  --about-top: 55%;
  --about-left: 45%;
  --about-heading-font-size: 25px;
  --about-text-font-size: 18px;
  --social-right: 40px;
  --social-bottom: 30px;
  --social-gap: 12px;
  --social-font-size: 20px;
  --mode-btn-right: 40px;
  --mode-btn-top: 20px;
  --mode-btn-font-size: 16px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html,
body {
  height: 100%;
}

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI",
    sans-serif;
  background: #000;
  color: #fff;
  overflow: hidden;
}

.hero {
  position: relative;
  width: 100vw;
  height: var(--hero-height);
  margin: 0;
  overflow: hidden;
}

.hero-bg {
  position: fixed;
  inset: 0;
  background-image: var(--bg-image);
  background-size: cover;
  background-position: center;
  filter: brightness(0.9);
  animation: bgDriftSlow var(--bg-duration-slow) ease-in-out infinite alternate;
  z-index: 0;
}

@keyframes bgDriftSlow {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(calc(var(--bg-shift-distance) * -1));
  }
}

@keyframes bgDriftFast {
  from {
    transform: translateX(0) scale(1);
    filter: brightness(1) blur(0px);
  }
  50% {
    transform: translateX(calc(var(--bg-shift-distance) * -2)) scale(1.03);
    filter: brightness(1.1) blur(1.5px);
  }
  to {
    transform: translateX(0) scale(1);
    filter: brightness(1) blur(0px);
  }
}

body.flash-mode .hero-bg {
  animation: bgDriftFast var(--bg-duration-fast) ease-in-out infinite;
}

.speed-layer {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 1;
  overflow: hidden;
}

.speed-particle {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 2px;
  height: 60px;
  background: rgba(255, 255, 255, 0.8);
  filter: blur(1px);
  opacity: 0;
  transform-origin: center center;
  --tx: 0px;
  --ty: 0px;
  --rot: 0deg;
  animation: speedBurst 0.6s linear forwards;
}

@keyframes speedBurst {
  0% {
    opacity: 0.9;
    transform: translate(-50%, -50%) rotate(var(--rot)) scaleY(0.3);
  }
  100% {
    opacity: 0;
    transform: translate(
        calc(-50% + var(--tx)),
        calc(-50% + var(--ty))
      )
      rotate(var(--rot))
      scaleY(1.1);
  }
}

.hero-logo {
  position: absolute;
  top: var(--logo-top);
  left: var(--logo-left);
  transform: translateX(-50%);
  width: var(--logo-width);
  max-width: 800px;
  z-index: 3;
  opacity: 0;
  transform-origin: center;
  animation: logoFadeIn 0.8s ease-out forwards 0.2s;
}

@keyframes logoFadeIn {
  from {
    opacity: 0;
    transform: translateX(-50%) translateY(10px) scale(0.97);
  }
  to {
    opacity: 1;
    transform: translateX(-50%) translateY(0) scale(1);
  }
}

.flash-character-main {
  position: absolute;
  width: var(--flash-width);
  left: var(--flash-left);
  bottom: var(--flash-bottom);
  z-index: 2;
  transform-origin: bottom center;
  animation: flashIdle 4s ease-in-out infinite;
  transition: opacity 0.25s ease;
}

@keyframes flashIdle {
  0%,
  100% {
    transform: translate(0, 0) rotate(0deg);
  }
  50% {
    transform: translate(0, -6px) rotate(-1deg);
  }
}

body.flash-mode .flash-character-main {
  opacity: 0;
}

.flash-character-center {
  position: absolute;
  width: var(--flash-center-width);
  top: 50%;
  left: 50%;
  transform: translate(-50%, -55%);
  z-index: 3;
  transform-origin: center bottom;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}

@keyframes flashRunCenter {
  0% {
    transform: translate(-50%, -55%) translateX(-4px) translateY(-2px) rotate(-4deg);
  }
  25% {
    transform: translate(-50%, -55%) translateX(4px) translateY(-4px) rotate(3deg);
  }
  50% {
    transform: translate(-50%, -55%) translateX(-5px) translateY(-1px) rotate(-3deg);
  }
  75% {
    transform: translate(-50%, -55%) translateX(5px) translateY(-3px) rotate(4deg);
  }
  100% {
    transform: translate(-50%, -55%) translateX(-4px) translateY(-2px) rotate(-4deg);
  }
}

body.flash-mode .flash-character-center {
  opacity: 1;
  pointer-events: auto;
  animation: flashRunCenter 0.25s linear infinite;
}

.about-block {
  position: absolute;
  top: var(--about-top);
  left: var(--about-left);
  width: var(--about-width);
  padding: 18px 20px;
  background: rgba(0, 0, 0, 0.55);
  backdrop-filter: blur(4px);
  border-radius: 16px;
  z-index: 2;
  transition: opacity 0.25s ease;
}

.about-heading {
  font-size: var(--about-heading-font-size);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 8px;
  color: #ffd85a;
}

.about-text {
  font-size: var(--about-text-font-size);
  line-height: 1.5;
}

body.flash-mode .about-block {
  opacity: 0;
  pointer-events: none;
}

.social-buttons {
  position: absolute;
  right: var(--social-right);
  bottom: var(--social-bottom);
  display: flex;
  gap: var(--social-gap);
  z-index: 3;
}

.social-btn {
  font-size: var(--social-font-size);
  padding: 10px 26px;
  border-radius: 18px;
  border: none;
  cursor: pointer;
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
  backdrop-filter: blur(6px);
  transition: transform 0.18s ease, background 0.18s ease,
    box-shadow 0.18s ease;
}

.social-btn:hover {
  transform: translateY(-2px);
  background: rgba(255, 255, 255, 0.25);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.35);
}

.mode-toggle-btn {
  position: absolute;
  top: var(--mode-btn-top);
  right: var(--mode-btn-right);
  padding: 10px 22px;
  font-size: var(--mode-btn-font-size);
  border-radius: 999px;
  border: 1px solid rgba(255, 255, 255, 0.5);
  background: radial-gradient(circle at top left,
    rgba(255, 200, 87, 0.35),
    rgba(0, 0, 0, 0.7));
  color: #fff;
  cursor: pointer;
  z-index: 4;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  transition: background 0.2s ease, transform 0.2s ease,
    box-shadow 0.2s ease, border-color 0.2s ease;
  display: flex;
  align-items: center;
  gap: 8px;
}

.mode-toggle-btn::before {
  content: "●";
  font-size: 10px;
  opacity: 0.7;
}

.mode-toggle-btn:hover:not(:disabled) {
  background: radial-gradient(circle at top left,
    rgba(255, 200, 87, 0.5),
    rgba(0, 0, 0, 0.8));
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
}

.mode-toggle-btn:disabled {
  opacity: 0.6;
  cursor: default;
}

body.flash-mode .mode-toggle-btn {
  border-color: #ffc857;
  box-shadow: 0 0 18px rgba(255, 200, 87, 0.9);
}

body.flash-mode .mode-toggle-btn::before {
  content: "⚡";
}

@media (max-width: 768px) {
  :root {
    --flash-width: 230px;
    --flash-left: 50%;
    --flash-bottom: 12%;

    --flash-center-width: 320px;

    --logo-width: 80%;
    --logo-top: 8%;
    --logo-left: 50%;

    --about-width: 86%;
    --about-top: 56%;
    --about-left: 50%;
  }

  .flash-character-main {
    transform: translateX(-50%);
  }

  .about-block {
    transform: translateX(-50%);
  }

  .social-buttons {
    right: 50%;
    bottom: 16px;
    transform: translateX(50%);
  }

  .mode-toggle-btn {
    top: 14px;
    right: 14px;
  }
}