:root {
    --bg: linear-gradient(135deg, #74ebd5, #acb6e5);
    --text: #000;
    --card: rgba(255, 255, 255, 0.25);
    --btn: #4CAF50;
    --btn-hover: #45a049;
    --error: #d60000;
}

/* 🌙 DARK MODE */
body.dark {
    --bg: #121212;
    --text: #ffffff;
    --card: rgba(255, 255, 255, 0.08);
    --btn: #2e7d32;
    --btn-hover: #1b5e20;
    --error: #ff4d4d;
}

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

/* BODY */
body {
    font-family: Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background 0.3s ease, color 0.3s ease;
    padding: 20px;
}

/* HEADER */
header {
    text-align: center;
    margin-top: 20px;
}

header h1 {
    margin-bottom: 10px;
}

header p {
    margin-bottom: 15px;
}

/* CALCULATOR CARD */
.container {
    margin: 30px auto;
    background: var(--card);
    backdrop-filter: blur(12px);
    padding: 30px;
    border-radius: 20px;
    width: 100%;
    max-width: 420px;
    text-align: center;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
}

/* INPUT */
input {
    padding: 12px;
    width: 100%;
    margin: 10px 0;
    border: none;
    border-radius: 8px;
    outline: none;
    font-size: 16px;
}

/* BUTTON */
button {
    padding: 12px 20px;
    border: none;
    border-radius: 8px;
    background: var(--btn);
    color: white;
    font-weight: bold;
    cursor: pointer;
    transition: 0.3s ease;
}

button:hover {
    background: var(--btn-hover);
}

/* RESULTS */
#result,
#birthday,
#lived,
#error {
    margin-top: 15px;
    font-weight: bold;
}

#error {
    color: var(--error);
}

/* CONTENT SECTIONS */
section {
    width: 100%;
    max-width: 800px;
    margin: 40px auto;
    line-height: 1.8;
}

section h2,
section h3 {
    margin-bottom: 15px;
}

section p {
    margin-bottom: 15px;
}

section ul {
    margin: 15px 0;
    padding-left: 25px;
}

section li {
    margin-bottom: 10px;
}

/* LINKS */
a {
    color: var(--text);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* FOOTER */
footer {
    margin-top: 40px;
    text-align: center;
    padding: 20px;
    font-size: 12px;
}

/* MOBILE */
@media (max-width: 768px) {
    .container {
        width: 95%;
        padding: 20px;
    }

    section {
        width: 95%;
    }

    header h1 {
        font-size: 30px;
    }
}/* BMI Calculator */

.bmi-box{
    max-width:500px;
    margin:40px auto;
    background:#fff;
    padding:30px;
    border-radius:15px;
    box-shadow:0 4px 15px rgba(0,0,0,0.1);
}

.bmi-box label{
    display:block;
    margin-top:15px;
    font-weight:bold;
}

.bmi-box input{
    width:100%;
    padding:12px;
    margin-top:5px;
    border:1px solid #ccc;
    border-radius:8px;
}

.bmi-box button{
    width:100%;
    margin-top:20px;
    padding:12px;
    border:none;
    border-radius:8px;
    cursor:pointer;
    font-size:16px;
}

#result{
    margin-top:20px;
    text-align:center;
}

#category{
    text-align:center;
    font-weight:bold;
}