:root {
  --header-bg: linear-gradient(135deg, #2c3e50, #34495e);
  --calc-bg: #ffffff;
  --btn-bg: #f3f4f6;
  --operator: #3b82f6;
  --equal: #10b981;
  --sci: #f59e0b;
  --memory: #8b5cf6;
}

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

body {
  font-family: 'Segoe UI', sans-serif;
  background: #f3f4f6;
}

/* Header */
.header {
  background: var(--header-bg);
  padding: 1rem;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}
.nav {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.nav-links {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}
.nav-links a {
  color: white;
  text-decoration: none;
  font-size: 0.95rem;
}
.logo {
  color: white;
  font-size: 1.5rem;
  font-weight: bold;
  text-decoration: none;
}

/* Main Layout */
.calculator-wrapper {
  max-width: 1200px;
  margin: 2rem auto;
  padding: 0 20px;
}
.calc-title {
  text-align: center;
  font-size: 1.8rem;
  color: #2c3e50;
  margin-bottom: 1rem;
}
.calculator-container {
  display: flex;
  justify-content: center;
}
.calculator {
  background: var(--calc-bg);
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
  padding: 2rem;
  width: 100%;
  max-width: 600px;
  text-align: center;
  border: 1px solid #e5e7eb;
}

.upload-btn {
  background: #2563eb;         /* Bright blue background */
  color: white;                /* White text */
  padding: 0.8rem 1.5rem;
  border-radius: 6px;
  font-size: 1rem;
  border: none;
  cursor: pointer;
  display: inline-block;
  margin-top: 1rem;
  transition: background 0.3s ease-in-out;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.15);
}

.upload-btn:hover {
  background: #1d4ed8;         /* Slightly darker blue on hover */
}


/* Progress Bar */
.progress-bar {
  width: 100%;
  height: 20px;
  background: #e2e8f0;
  border-radius: 10px;
  margin-top: 1rem;
  overflow: hidden;
}
.progress {
  height: 100%;
  width: 0%;
  background: #10b981;
  transition: width 0.4s ease-in-out;
}

/* Footer */
.footer {
  background: var(--header-bg);
  color: white;
  padding: 2rem;
  text-align: center;
  margin-top: 3rem;
}
.footer-links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 1rem;
}
.footer-links a {
  color: white;
  text-decoration: none;
  font-size: 0.9rem;
}