:root {
  /* ---------- Header Colors (project blue palette) ---------- */
  --header-bg-color: #4f46e5;        /* dark blue background */
  --header-text-color: #ffffff;      /* white text */
  --header-subtext-color: #cbd5e1;   /* light blue subtitle */
  --nav-link-color: #ffffff;         /* white nav links */
  --nav-link-hover-color: #93c5fd;   /* light blue hover */
  --lang-btn-bg: #ffffff;            
  --lang-btn-color: #4f46e5;         
  --header-btn-bg: #ffffff;          
  --header-btn-bg-hover: #3b82f6;    /* darker blue hover */
  --header-btn-text: #4f46e5;        

  /* ---------- Header Sizes ---------- */
  --header-padding: 1rem 2rem;
  --header-gap: 10px;
  --header-font-size: 3rem;
  --subheader-font-size: 1.5rem;
  --nav-font-size: 1.1rem;
  --header-btn-x_size: 80px;       /* default button size */
  --header-btn-y_size: 45px;       /* default button size */
  --header-btn-x_size-mobile: 40px; /* smaller on mobile */
  --header-btn-y_size-mobile: 40px; /* smaller on mobile */
  --lang-btn-padding: 0.3rem 0.7rem;
  --header-btn-padding: 0.5rem 1rem;
  --header-btn-radius: 5px;

  /* ---------- Breakpoints ---------- */
  --mobile-breakpoint: 768px;
}

/* -----------------------
   Header grid container
------------------------*/
.header_grid {
  display: grid;
  grid-template-columns: 1fr 2fr 2fr;
  grid-template-rows: auto auto;
  gap: var(--header-gap);
  align-items: center;
  padding: var(--header-padding);
  background-color: var(--header-bg-color);
  color: var(--header-text-color);
}

/* -----------------------
   Grid items placement
------------------------*/
.header_lang-btn {
  grid-row: 1 / span 2;
  grid-column: 1 / 2;
  background-color: var(--lang-btn-bg);
  color: var(--lang-btn-color);
  width: var(--header-btn-x_size);
  height: var(--header-btn-y_size);
  border: none;
  padding: var(--lang-btn-padding);
  cursor: pointer;
  border-radius: var(--header-btn-radius);
}

.header_main-title {
  grid-row: 1 / 2;
  grid-column: 2 / 3;
  text-align: center;
  font-size: var(--header-font-size);
}

.header_sub-title {
  grid-row: 2 / 3;
  grid-column: 2 / 3;
  text-align: center;
  font-weight: normal;
  font-size: var(--subheader-font-size);
  color: var(--header-subtext-color);
}

.header_mini-nav {
  grid-row: 1 / 2;
  grid-column: 3 / 4;
  justify-self: end;
}

.header_mini-nav a {
  color: var(--nav-link-color);
  margin-left: 1rem;
  text-decoration: none;
  font-size: var(--nav-font-size);
}

.header_mini-nav a:hover {
  color: var(--nav-link-hover-color);
}

.header_btn {
  grid-row: 2 / 3;
  grid-column: 3 / 4;
  justify-self: end;
  padding: var(--header-btn-padding);
  background-color: var(--header-btn-bg);
  color: var(--header-btn-text);
  text-decoration: none;
  border-radius: var(--header-btn-radius);
  font-weight: bold;
  transition: background-color 0.3s ease;
}

.header_btn:hover {
  background-color: var(--header-btn-bg-hover);
}

/* -----------------------
   Responsive design
------------------------*/
@media (max-width: 768px) {
  .header_grid {
    display: grid;
    /* Two columns:
       - Left: navigation (flexible)
       - Right: language button (auto width) */
    grid-template-columns: 1fr auto;

    /* Three rows:
       1 — nav + lang button
       2 — main title
       3 — subtitle */
    grid-template-rows: auto auto auto;

    gap: calc(var(--header-gap) / 2);
    align-items: center;
  }

  /* --- Row 1: navigation on the left --- */
  .header_mini-nav {
    grid-column: 1;   /* left side */
    grid-row: 1;
    justify-self: start;
  }

  /* --- Row 1: language button on the right --- */
  .header_lang-btn {
    grid-column: 2;   /* right side */
    grid-row: 1;
    justify-self: end;

    width: var(--header-btn-x_size-mobile);
    height: var(--header-btn-y_size-mobile);
  }

  /* --- Row 2: main title centered --- */
  .header_main-title {
    grid-column: 1 / -1; /* span both columns */
    grid-row: 2;
    text-align: center;
    justify-self: center;
  }

  /* --- Row 3: subtitle centered --- */
  .header_sub-title {
    grid-column: 1 / -1; /* span both columns */
    grid-row: 3;
    text-align: center;
    justify-self: center;
  }

  /* Optional: action button (if included) */
  .header_btn {
    grid-column: 1 / -1;
    grid-row: 4;
    justify-self: center;
  }
}