/* =========================
   General Reset & Variables
   ========================= */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --primary-color: #4CAF50;
  --secondary-color: #3498db;
  --accent-color: #e91e63;
  --background-color: #f9f9f9;
  --dark-text-color: #333;
  --white-color: #fff;

  --padding-small: 10px;
  --padding-medium: 15px;
  --padding-large: 20px;

  --transition-speed: 0.3s;
}

/* =========================
   Mobile-First Base Styles
   ========================= */
body {
  font-family: 'Open Sans', Arial, sans-serif;
  background-color: var(--background-color);
  color: var(--dark-text-color);
  line-height: 1.6;
  font-size: 16px;
  margin: 0;
  overflow-x: hidden;
}

/* Header */
header {
  background-color: var(--primary-color);
  color: var(--white-color);
  padding: var(--padding-medium);
  display: flex;
  flex-direction: column;
  align-items: center;
}
header .logo {
  display: flex;
  align-items: center;
  justify-content: center;
}
header .logo img {
  width: 50px;
  height: auto;
  margin-right: var(--padding-small);
}
header nav {
  margin-top: var(--padding-small);
  display: flex;
  gap: var(--padding-small);
  flex-wrap: wrap;
}
header nav a {
  color: var(--white-color);
  text-decoration: none;
  font-weight: bold;
  padding: var(--padding-small);
  transition: background-color var(--transition-speed);
}
header nav a:hover {
  background-color: var(--accent-color);
  border-radius: 4px;
}

/* Main Content */
main {
  padding: var(--padding-medium);
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 70vh;
}
.navigation-column {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--padding-medium);
  width: 100%;
  max-width: 400px;
}
.navigation-column a {
  background-color: var(--primary-color);
  color: var(--white-color);
  text-align: center;
  padding: var(--padding-medium);
  text-decoration: none;
  border-radius: 5px;
  transition: background-color var(--transition-speed);
}
.navigation-column a:hover {
  background-color: var(--accent-color);
}

/* Footer */
footer {
  background-color: var(--primary-color);
  color: var(--white-color);
  text-align: center;
  padding: var(--padding-medium);
}

/* Flexible Images */
img {
  max-width: 100%;
  height: auto;
}

/* Specific rule for the preview image */
#previewImage {
  display: none;  /* Hidden by default */
  width: 100px;   /* Fixed width */
  max-width: 100px;
  height: auto;   /* Maintain aspect ratio */
  border-radius: 8px;
  box-shadow: 0 0 5px rgba(0,0,0,0.3);
}

/* =========================
   Media Queries for Desktop
   ========================= */
@media (min-width: 600px) {
  header {
    flex-direction: row;
    justify-content: space-between;
  }
  main {
    padding: var(--padding-large);
  }
  .navigation-column {
    grid-template-columns: repeat(2, 1fr);
    max-width: 800px;
  }
}
@media (min-width: 900px) {
  .navigation-column {
    grid-template-columns: repeat(3, 1fr);
    max-width: 1000px;
  }
}