/* reset */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Inter', sans-serif;
  -webkit-tap-highlight-color: transparent;
}

/* base */
body {
  background: linear-gradient(135deg, #eef1ff, #f8f9ff);
  color: #1c1c1c;
  min-height: 100vh;
  overflow-x: hidden;
  transition: background 0.4s ease, color 0.4s ease;
}

/* soft blur background */
.background-blur {
  position: fixed;
  width: 280px;
  height: 280px;
  background: #9aa8ff;
  filter: blur(160px);
  opacity: 0.45;
  top: -100px;
  left: -100px;
  z-index: -1;
}

/* container - mobile first */
.container {
  width: 100%;
  max-width: 720px;
  margin: 0 auto;
  padding: 28px 20px 80px 20px;
}

/* header */
header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 50px;
}

h1 {
  font-size: 22px;
  font-weight: 600;
  letter-spacing: -0.3px;
}

/* button */
button {
  padding: 8px 16px;
  border-radius: 999px;
  border: none;
  cursor: pointer;
  background: #1c1c1c;
  color: white;
  font-size: 12px;
  transition: all 0.25s ease;
}

button:active {
  transform: scale(0.95);
}

/* chapter card */
.chapter {
  margin-bottom: 50px;
  padding: 22px 20px;
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.65);
  backdrop-filter: blur(14px);
  box-shadow: 0 8px 25px rgba(0,0,0,0.06);

  opacity: 0;
  transform: translateY(25px);
  transition: all 0.6s ease;
}

.chapter.visible {
  opacity: 1;
  transform: translateY(0);
}

/* chapter title */
h2 {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: #666;
  margin-bottom: 16px;
}

/* paragraph */
.content p {
  font-size: 15px;
  line-height: 1.9;
  margin-bottom: 14px;
}

/* quote block */
.quote {
  margin-top: 18px;
  padding: 16px 18px;
  border-radius: 14px;
  background: rgba(0, 0, 0, 0.04);
  font-size: 14px;
  line-height: 1.8;
  font-style: italic;
}

/* footer watermark */
footer {
  margin-top: 70px;
  text-align: center;
  font-size: 12px;
  opacity: 0.6;
}

/* ========================= */
/* desktop enhancement */
/* ========================= */

@media (min-width: 768px) {

  .container {
    padding: 80px 40px;
  }

  h1 {
    font-size: 28px;
  }

  .chapter {
    padding: 30px 32px;
  }

  .content p {
    font-size: 16px;
  }
}

/* ========================= */
/* dark mode */
/* ========================= */

body.dark {
  background: linear-gradient(135deg, #0f0f14, #1a1a22);
  color: #f2f2f2;
}

body.dark .chapter {
  background: rgba(25, 25, 30, 0.75);
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
}

body.dark .quote {
  background: rgba(255,255,255,0.05);
}

body.dark button {
  background: #f2f2f2;
  color: #111;
}