/* ===================================
           BASE: rem is relative to root font size
           Users can change this in browser settings
           =================================== */
html {
  font-size: 100%; /* 1rem = 16px (default browser) */
}

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

body {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
  color: #eee;
  padding: 20px;
  line-height: 1.6;

  /* ===================================
               FLUID BODY TEXT (scales smoothly)
               min: 16px | preferred: 2vw | max: 20px
               =================================== */
  font-size: clamp(1rem, 1rem + 0.5vw, 1.25rem);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
}

/* ===================================
           FLUID HEADINGS (scale with screen)
           =================================== */
h1 {
  /* min: 28px, preferred: 5vw, max: 48px */
  font-size: clamp(1.75rem, 2rem + 3vw, 3rem);
  text-align: center;
  margin-bottom: 0.5rem;
  background: linear-gradient(135deg, #fff, #4a90e2);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.subtitle {
  text-align: center;
  color: #aaa;
  margin-bottom: 2rem;
  font-size: clamp(0.875rem, 0.875rem + 0.5vw, 1.125rem);
}

/* ===================================
           THEORY SECTION
           =================================== */
.theory {
  background-color: #0a0a1a;
  border-radius: 1rem;
  padding: 1.5rem;
  margin-bottom: 2rem;
}

.theory h2 {
  color: #4a90e2;
  margin-bottom: 1rem;
  font-size: clamp(1.25rem, 1.25rem + 1vw, 1.75rem);
}

.theory h3 {
  color: #e94560;
  margin: 1.5rem 0 0.75rem;
  font-size: clamp(1rem, 1rem + 0.5vw, 1.25rem);
}

.theory p {
  color: #ccc;
  line-height: 1.6;
  margin-bottom: 1rem;
}

.theory ul {
  margin-left: 1.5rem;
  color: #ccc;
  line-height: 1.8;
}

.theory code {
  background-color: #1a1a2e;
  padding: 0.125rem 0.375rem;
  border-radius: 0.25rem;
  color: #82b1ff;
}

/* ===================================
           DEMO SECTIONS
           =================================== */
.demo-section {
  background-color: #0f3460;
  border-radius: 1rem;
  padding: 1.5rem;
  margin-bottom: 2rem;
}

.demo-section h3 {
  color: #4a90e2;
  margin-bottom: 1rem;
  font-size: clamp(1.125rem, 1.125rem + 0.5vw, 1.375rem);
}

/* ===================================
           COMPARISON BOXES
           =================================== */
.comparison {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  margin-top: 1rem;
}

.comparison-card {
  background-color: #1a1a2e;
  border-radius: 0.75rem;
  padding: 1.5rem;
  flex: 1;
  min-width: 200px;
}

.comparison-card h4 {
  color: #e94560;
  margin-bottom: 1rem;
}

.fixed-px {
  font-size: 16px; /* Fixed pixels — does not scale */
}

.fixed-rem {
  font-size: 1rem; /* 16px, but scales with user settings */
}

.fluid-clamp {
  font-size: clamp(0.875rem, 1rem + 1vw, 1.5rem);
}

.demo-text {
  background-color: #0f3460;
  padding: 1rem;
  border-radius: 0.5rem;
  margin-top: 0.5rem;
}

/* ===================================
           CODE BLOCK
           =================================== */
.code-block {
  background-color: #0a0a1a;
  padding: 1rem;
  border-radius: 0.75rem;
  font-family: "Courier New", monospace;
  font-size: 0.8rem;
  color: #82b1ff;
  overflow-x: auto;
  margin-top: 1rem;
}

/* ===================================
           REM VS PX DEMO
           =================================== */
.rem-demo {
  background-color: #1a1a2e;
  border-radius: 0.75rem;
  padding: 1rem;
  margin-top: 1rem;
}

.rem-demo p {
  margin: 0.5rem 0;
}

/* ===================================
           FLUID SPACING DEMO
           =================================== */
.fluid-spacing {
  margin-bottom: clamp(1rem, 3vw, 3rem);
  padding: clamp(0.5rem, 2vw, 2rem);
  background-color: #1a1a2e;
  border-radius: 0.75rem;
  text-align: center;
}

footer {
  text-align: center;
  padding: 2rem;
  color: #666;
  font-size: 0.875rem;
}

@media (min-width: 768px) {
  body {
    padding: 40px;
  }
}