* {
  font-family: Arial, Helvetica, sans-serif;
  box-sizing: border-box;

  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

html,
body {
  margin: 0;
  border: 0;
  padding: 0;
  background-color: #ffffff;

  font-size: 16px;
  line-height: 1.6;
  color: #111;
  letter-spacing: 0.02em;

  height: 100%;
}

body {
  font-weight: 400;

  display: flex;
  flex-direction: column;
}

header {
  width: 100%;
  background-color: #ffffff;
}

.header-inner {
  margin: auto;
  width: 50%;
  max-width: 900px;
  padding: 20px;
  text-align: center;
  border-bottom: 1px solid #ffffff;
  letter-spacing: 0.05em;
  font-weight: 500;
}

main {
  margin: auto;
  width: 50%;
  max-width: 900px;
  padding: 20px;
  flex: 1;

  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
}

main > h1 {
  text-align: center;
  font-size: 3.5em;
  margin: 0;
  font-weight: 600;
  letter-spacing: 0.06em;
  line-height: 1.2;
}

main > h2 {
  text-align: center;
  font-size: 1.5em;
  margin: 0;
  font-weight: 500;
  letter-spacing: 0.04em;
  line-height: 1.3;
}

main > p {
  text-align: center;
  font-size: 0.9em;
  margin: 0;
  line-height: 1.7;
  letter-spacing: 0.03em;
  max-width: 65ch;
}

.placeholder-button {
  display: flex;
  align-items: center;
  justify-content: center;

  width: 100%;
  min-height: 100vh;

  margin: 0;
  padding: 20px;

  font-size: 1.1rem;
  font-weight: 500;
  letter-spacing: 0.06em;

  color: #ffffff;
  background-color: #000000;
  border: 1px solid #000000;
  border-radius: 8px;

  text-decoration: none;
  cursor: default;
  user-select: none;

  box-shadow: 0 4px 16px rgba(255, 255, 255, 0.08);

  transition: all 0.2s ease;
}

.placeholder-button:hover {
  box-shadow: 0 6px 20px rgba(255, 255, 255, 0.12);
  border-color: #111111;
}

@media (max-width: 768px) {
  .placeholder-button {
    min-height: 100svh;
  }
}

a:link,
a:visited {
  color: blue;
  background-color: transparent;
  text-decoration: underline;
  text-decoration-color: black;
  text-underline-offset: 2px;
}

a:hover {
  color: red;
  background-color: transparent;
  text-decoration: underline;
  text-decoration-color: black;
  text-underline-offset: 3px;
}

a:active {
  color: green;
  background-color: transparent;
  text-decoration: underline;
  text-decoration-color: black;
}

r {
  color: red;
}

g {
  color: green;
}

b {
  color: blue;
}

v {
  color: black;
}

footer {
  margin: auto;
  width: 50%;
  max-width: 900px;
  padding: 20px;
  text-align: center;
  border-top: 1px solid #ffffff;
  color: #555;

  font-size: 0.95rem;
  line-height: 1.7;
  letter-spacing: 0.06em;
}

.footer-column {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  text-align: center;
  margin: 18px 0;
  gap: 12px;
}

.footer-col {
  font-size: 0.95em;
  font-weight: 500;
  letter-spacing: 0.04em;
}

footer > h1 {
  text-align: center;
  font-size: 3.5em;
  margin: 5px 0;
  font-weight: 600;
  letter-spacing: 0.06em;
  line-height: 1.2;
}

footer > h2 {
  text-align: center;
  font-size: 1.5em;
  margin: 5px 0;
  font-weight: 500;
  letter-spacing: 0.04em;
  line-height: 1.3;
}

footer > p {
  text-align: center;
  font-size: 0.85em;
  margin: 6px 0;
  line-height: 1.7;
  letter-spacing: 0.05em;
}

footer > p:first-child {
  font-weight: 500;
  letter-spacing: 0.15em;
}

.fixed-button {
  position: fixed;
  bottom: 20px;
  left: 50%;
  transform: translateX(-50%);

  padding: 10px 18px;
  font-size: 0.9rem;
  font-weight: 500;
  letter-spacing: 0.06em;

  color: #111;
  background-color: #ffffff;
  border: 1px solid #e0e0e0;
  border-radius: 6px;

  cursor: pointer;
  text-decoration: none;
  text-align: center;

  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);

  transition: all 0.2s ease;
  z-index: 1000;
}

.fixed-button:hover {
  transform: translateX(-50%) translateY(-2px);
  border-color: #bdbdbd;
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.12);
}

.fixed-button:active {
  transform: translateX(-50%) translateY(0px);
  box-shadow: 0 3px 8px rgba(0, 0, 0, 0.1);
}

.side-button {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);

  width: 48px;
  height: 48px;

  display: flex;
  align-items: center;
  justify-content: center;

  font-size: 1.2rem;
  font-weight: 600;
  letter-spacing: 0.04em;

  color: #111;
  background-color: #ffffff;
  border: 1px solid #e0e0e0;
  border-radius: 8px;

  text-decoration: none;
  cursor: pointer;
  user-select: none;

  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);

  transition: all 0.2s ease;
  z-index: 1000;
}

.side-button.left {
  left: 20px;
}

.side-button.right {
  right: 20px;
}

.side-button:hover {
  transform: translateY(-50%) scale(1.05);
  border-color: #bdbdbd;
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.12);
}

.side-button:active {
  transform: translateY(-50%) scale(0.98);
  box-shadow: 0 3px 8px rgba(0, 0, 0, 0.1);
}

@media (max-width: 768px) {
  .header-inner {
    width: 90%;
  }
}

@media (max-width: 768px) {
  main,
  footer {
    width: 90%;
  }

  .footer-columns {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  main > h1 {
    font-size: 2.4em;
    letter-spacing: 0.05em;
  }

  main > h2 {
    font-size: 1.3em;
  }
}

@media (max-width: 768px) {
  .fixed-button {
    bottom: 16px;
    width: calc(100% - 40px);
    max-width: 320px;
  }
}

@media (max-width: 768px) {
  .side-button {
    width: 42px;
    height: 42px;
    font-size: 1.1rem;
  }

  .side-button.left {
    left: 12px;
  }

  .side-button.right {
    right: 12px;
  }
}