:root {
  --light-bg: #f5f5f7;
  --dark-bg: #1b1b32;
  --primary: #fecc4c;
  --primary-dark: #feac32;
  --success: #acd157;
  --danger: #ff6b6b;
  --text-light: #ffffff;
  --text-dark: #111;
  --border-radius: 8px;
  --transition: 0.3s ease;
  --font: 'Lato', Helvetica, Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  font-family: var(--font);
  background-color: var(--dark-bg);
  color: var(--text-light);
  margin: 0;
  transition: background-color var(--transition), color var(--transition);
}

h1 {
  text-align: center;
  margin-top: 20px;
  font-size: 2.2rem;
}

.theme-btn {
  display: block;
  margin: 10px auto 20px;
  padding: 8px 16px;
  border: none;
  border-radius: var(--border-radius);
  background: linear-gradient(45deg, var(--primary), var(--primary-dark));
  color: var(--text-dark);
  font-weight: bold;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.theme-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
}

.container {
  width: 90%;
  max-width: 700px;
  margin: 0 auto 40px;
  background-color: rgba(0,0,0,0.3);
  padding: 20px;
  border-radius: var(--border-radius);
  box-shadow: 0 8px 20px rgba(0,0,0,0.3);
  transition: background-color var(--transition);
}

label, legend {
  font-weight: bold;
}

input, select {
  width: 100%;
  padding: 8px 10px;
  border-radius: var(--border-radius);
  border: 1px solid #ccc;
  margin-bottom: 12px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

input:focus, select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 6px var(--primary);
  outline: none;
}

button {
  padding: 10px 16px;
  margin-right: 10px;
  border: none;
  border-radius: var(--border-radius);
  background: var(--primary);
  color: var(--text-dark);
  font-weight: bold;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

button:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
}

fieldset {
  border-radius: var(--border-radius);
  border: 2px solid #ccc;
  padding: 15px;
  margin-bottom: 20px;
  transition: border-color var(--transition);
}

.output {
  margin-top: 20px;
  background: rgba(0,0,0,0.2);
  padding: 15px;
  border-radius: var(--border-radius);
  text-align: center;
  transition: background-color var(--transition);
}

.progress-bar {
  width: 100%;
  height: 12px;
  background: #ddd;
  border-radius: var(--border-radius);
  overflow: hidden;
  margin-bottom: 12px;
}

.progress {
  height: 100%;
  width: 0%;
  background: var(--success);
  transition: width 0.5s ease, background var(--transition);
}

.surplus {
  color: var(--danger);
  font-weight: bold;
}

.deficit {
  color: var(--success);
  font-weight: bold;
}

.hide {
  display: none;
}

.entry-controls {
  display: flex;
  gap: 10px;
  margin-top: 8px;
}

.buttons {
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
}

.buttons button {
  flex: 1 1 48%;
  margin-bottom: 10px;
}

/* Light Mode */
body.light-mode {
  background-color: var(--light-bg);
  color: var(--text-dark);
}

body.light-mode .container {
  background-color: #fff;
  box-shadow: 0 4px 20px rgba(0,0,0,0.1);
}

body.light-mode fieldset {
  border-color: #ccc;
}

body.light-mode .output {
  background-color: #f0f0f0;
}

/* Responsive */
@media(max-width: 600px) {
  h1 { font-size: 1.8rem; }
  .entry-controls {
    flex-direction: column;
  }
  .buttons button { flex: 1 1 100%; }
}