/* ==============================
   Base Variables & Resets
   ============================== */
:root {
  /* Grayscale palette */
  --gray-100: #f8f9fa;
  --gray-200: #e9ecef;
  --gray-300: #dee2e6;
  --gray-400: #ced4da;
  --gray-500: #adb5bd;
  --gray-600: #6c757d;
  --gray-700: #495057;
  --gray-800: #343a40;
  --gray-900: #212529;
  --white:    #ffffff;
  --black:    #212529; /* softer than pure black */
  
  /* Spacing & sizes */
  --spacer:        1rem;
  --spacer-sm:     .5rem;
  --border-radius: .5rem;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.06), 0 1px 3px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 8px rgba(0,0,0,0.08), 0 2px 4px rgba(0,0,0,0.06);
  
  /* Animation speed */
  --transition-speed: .15s;
}

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

html {
  font-family: 'Inter', sans-serif;
  font-size: 16px;
  background: var(--gray-100);
  color: var(--gray-800);
}

body {
  margin: 0;
  /* reserve space for bottom nav on all viewports */
  padding-bottom: 4rem;
}

.container {
  max-width: 480px;
  margin: 0 auto;
  /* initial padding, will adjust in media queries */
  padding: 2rem 1rem;
}

/* ==============================
   Card & Form Elements
   ============================== */
.card {
  background: var(--white);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-speed);
  overflow: hidden;
  margin-bottom: var(--spacer);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

.card-header {
  background: var(--gray-200);
  padding: var(--spacer);
  font-weight: 600;
  font-size: 1.25rem;
  color: var(--gray-900);
}

.card-body {
  padding: var(--spacer);
}

.card-body label {
  display: block;
  margin-bottom: var(--spacer-sm);
  font-weight: 500;
  color: var(--gray-700);
}

.card-body input,
.card-body select,
.card-body textarea {
  width: 100%;
  padding: .75rem;
  margin-bottom: var(--spacer);
  border: 1px solid var(--gray-400);
  border-radius: var(--border-radius);
  transition: border-color var(--transition-speed), box-shadow var(--transition-speed);
}

.card-body input:focus,
.card-body select:focus,
.card-body textarea:focus {
  border-color: var(--gray-700);
  box-shadow: 0 0 0 3px rgba(52,58,64,0.15);
  outline: none;
}

/* ==============================
   Buttons
   ============================== */
.btn {
  display: block;
  width: 100%;
  padding: .75rem;
  background: var(--black);
  color: var(--white);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: .5px;
  border: none;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: transform .1s ease, box-shadow var(--transition-speed);
}

.btn:hover {
  box-shadow: 0 2px 12px rgba(0,0,0,0.1);
}

.btn:active {
  transform: scale(.98);
}

/* ==============================
   Bottom Navigation
   ============================== */
.bottom-nav {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  display: flex;
  height: 4rem;
  background: var(--white);
  border-top: 1px solid var(--gray-300);
  box-shadow: 0 -1px 4px rgba(0,0,0,0.06);
  z-index: 50;
}

.bottom-nav .nav-link {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  color: var(--gray-600);
  transition: color var(--transition-speed);
  font-size: .8125rem; /* 13px */
}

.bottom-nav .nav-link.active {
  color: var(--black);
}

.bottom-nav .nav-icon {
  width: 24px;
  height: 24px;
  margin-bottom: .25rem;
  stroke: currentColor;
  fill: none;
  stroke-width: 2;
}

/* ==============================
   Mobile Adjustments
   ============================== */
@media (max-width: 480px) {
  /* Slightly smaller base font for balance */
  html {
    font-size: 17px;
  }

  /* Container padding */
  .container {
    padding: 1rem 0.75rem;
  }

  /* Card header */
  .card-header {
    padding: 1rem 0.75rem;
    font-size: 1.25rem;
  }

  /* Card body */
  .card-body {
    padding: 1rem;
  }

  /* Labels */
  .card-body label {
    margin-bottom: .5rem;
    font-size: .9375rem; /* 15px */
  }

  /* Inputs */
  .card-body input,
  .card-body select,
  .card-body textarea {
    padding: .75rem;
    margin-bottom: 1rem;
    font-size: .9375rem; /* 15px */
  }

  /* Buttons */
  .btn {
    padding: .75rem;
    font-size: .9375rem; /* 15px */
  }

  /* Bottom nav */
  .bottom-nav {
    height: 4rem;
  }
  .bottom-nav .nav-link {
    font-size: .8125rem; /* 13px */
  }
  .bottom-nav .nav-icon {
    width: 24px;
    height: 24px;
    margin-bottom: .25rem;
  }

  /* Keep space for nav */
  body {
    padding-bottom: 4rem;
  }
}