:root {
  
  --primary: #1b4d3e; 
  --bg-color: #1b4d3e; 
  --card-bg: #f1f8e9; 
  --accent: #c5a059; 
  --error-color: #d32f2f; 
}

* {
  box-sizing: border-box;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

body {
  margin: 0;
  padding: 0;
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-color); 
  padding-top: 120px; 
  height: 100vh; 
}

.navbar {
  height: var(--header-height);
  background-color: #ffffff;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  position: fixed;
  top: 0;
  width: 100%;
  z-index: 1000;
}

.navbar-container {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 100%;
  padding: 0 20px;
}

.logo {
  height: 50px;
  width: auto;
}
.logo-right {
  height: 55px;
  width: auto;
  margin-left: 20px;
}

.navbar-menu {
  display: flex;
  gap: 25px;
}
.nav-link {
  text-decoration: none;
  color: var(--secondary);
  font-weight: 600;
  font-size: 0.9rem;
  text-transform: uppercase;
}

.hamburger {
  display: none;
  font-size: 1.8rem;
  cursor: pointer;
  color: var(--secondary);
}

.mobile-menu {
  position: fixed;
  top: var(--header-height);
  left: 0;
  width: 100%;
  background: white;
  padding: 20px;
  box-shadow: 0 10px 10px rgba(0, 0, 0, 0.05);
  transform: translateY(-150%);
  transition: transform 0.3s ease-in-out;
  z-index: 999;
  flex-direction: column;
  gap: 15px;
  display: flex;
}
.mobile-menu.open {
  transform: translateY(0);
}

.container {
  max-width: 400px;
  margin: 0 auto;
  padding: 0 15px;
}

.calculator-card {
  background-color: var(--card-bg, #f1f8e9); 
  border-radius: 40px 10px 40px 10px; 
  padding: 30px;
  box-shadow: -10px 10px 0px var(--accent, #c5a059); 
  border: none;
}

.calc-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--primary, #1b4d3e); 
  margin-bottom: 20px;
  font-size: 0.95rem;
  font-weight: 800;
  letter-spacing: 1px;
}

#display {
  width: 100%;
  height: 80px;
  background-color: #ffffff;
  border: 2px solid #b0bec5;
  border-radius: 10px;
  margin-bottom: 20px;
  text-align: right;
  padding: 10px 20px;
  font-size: 2.5rem;
  font-family: "Consolas", monospace;
  color: var(--primary);
  outline: none;
  transition: all 0.3s ease;
}

#display:focus {
  border-color: var(--accent); 
}

.btn-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

button {
  border: none;
  height: 60px;
  border-radius: 12px;
  font-size: 1.2rem;
  font-weight: 700;
  cursor: pointer;
  transition:
    transform 0.1s,
    box-shadow 0.2s;
  box-shadow: 0 4px 0 rgba(0, 0, 0, 0.15);
}

button:active {
  transform: translateY(4px);
  box-shadow: none;
}

.btn-num {
  background-color: #ffffff;
  color: var(--primary, #1b4d3e); 
  border: 1px solid #e2e8f0;
}

.btn-op {
  background-color: var(--primary, #1b4d3e); 
  color: var(--accent, #c5a059); 
  font-size: 1.6rem;
}
.btn-func {
  background-color: rgba(27, 77, 62, 0.15); 
  color: var(--primary, #1b4d3e);
  font-weight: 800;
}

.btn-clear {
  background-color: #d32f2f; 
  color: white;
}

.btn-equal {
  background-color: var(--accent, #c5a059); 
  color: var(--primary, #1b4d3e); 
  font-size: 2rem;
  grid-column: span 1;
}

.btn-zero {
  grid-column: span 2;
}

@media (max-width: 768px) {
  .navbar-menu,
  .logo-right {
    display: none;
  }
  .hamburger {
    display: block;
  }
  .logo {
    height: 40px;
  }
  button {
    height: 55px;
    font-size: 1.1rem;
  }
}