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

:root {
  --bg: #0d0d0d;
  --card: #1a1a1a;
  --fg: #f0f0f0;
  --accent: #00b894;
  --accent-hover: #00a383;
  --dim: #888;
  --radius: 10px;
  --font: system-ui, sans-serif;
}

body {
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font);
  line-height: 1.6;
  min-height: 100vh;
}

/* Header Navigation */
nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  background: #111;
  padding: 1rem;
  gap: 1rem;
}

nav a {
  color: var(--fg);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}

nav a:hover {
  color: var(--accent);
}

/* Main layout */
main {
  max-width: 900px;
  margin: auto;
  padding: 2rem;
}

/* Headings */
h1, h2, h3 {
  color: var(--accent);
  margin-bottom: 1rem;
}

h1 {
  font-size: 2.2rem;
}

h2 {
  font-size: 1.6rem;
}

h3 {
  font-size: 1.2rem;
}

/* Footer */
footer {
  text-align: center;
  padding: 1rem;
  margin-top: 3rem;
  color: var(--dim);
  background: #111;
}

/* Buttons */
button {
  background: var(--accent);
  color: var(--bg);
  border: none;
  padding: 0.7rem 1.3rem;
  border-radius: var(--radius);
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.3s;
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

button:hover:not(:disabled) {
  background: var(--accent-hover);
}

/* Cards & Sections */
.card, section, .result {
  background: var(--card);
  padding: 2rem;
  border-radius: var(--radius);
  box-shadow: 0 4px 10px rgba(0,0,0,0.3);
  margin-bottom: 2rem;
}

/* Input Options */
.options {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.options label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1rem;
  cursor: pointer;
}

.options input {
  margin: 0;
}

/* Progress bar */
progress {
  width: 100%;
  height: 14px;
  margin-bottom: 1rem;
  border-radius: 7px;
  background: #333;
  overflow: hidden;
}
progress::-webkit-progress-bar {
  background-color: #222;
}
progress::-webkit-progress-value {
  background-color: var(--accent);
}
progress::-moz-progress-bar {
  background-color: var(--accent);
}

/* Axis Bar Chart */
.bar {
  height: 18px;
  background: var(--accent);
  border-radius: 9px;
  margin: 0.4rem 0;
}

.axis-label {
  display: flex;
  justify-content: space-between;
  font-size: 0.9rem;
  color: var(--dim);
}

/* Responsive tweaks */
@media (max-width: 600px) {
  nav {
    flex-direction: column;
    align-items: center;
  }

  .options {
    grid-template-columns: 1fr;
  }
}