/* Global Design Foundation (shared by pages that link this file) */
:root {
    --bg-gradient: linear-gradient(135deg, #e0eafc 0%, #cfdef3 100%);
    --card-bg: rgba(255, 255, 255, 0.8);
    --text-main: #1a202c;
    --text-muted: #4a5568;
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --border-color: rgba(255, 255, 255, 0.5);
    --shadow: 0 8px 32px rgba(31, 38, 135, 0.1);
}
.dark-mode {
    --bg-gradient: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    --card-bg: rgba(30, 41, 59, 0.7);
    --text-main: #f1f5f9;
    --text-muted: #cbd5e1;
    --border-color: rgba(255, 255, 255, 0.1);
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
}
* { box-sizing: border-box; margin: 0; padding: 0; -webkit-tap-highlight-color: transparent; }
body {
    font-family: 'Poppins', sans-serif;
    background: var(--bg-gradient);
    color: var(--text-main);
    min-height: 100vh;
    transition: background .5s;
}
header {
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    padding: 15px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 1000;
}
.logo {
    font-size: 1.6rem; font-weight: 700;
    background: linear-gradient(to right, #6366f1, #8b5cf6);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
    text-decoration: none;
}
.theme-btn { background: none; border: none; font-size: 1.4rem; cursor: pointer; color: var(--text-main); }
.container { max-width: 800px; margin: 0 auto; padding: 30px 20px; }
.hero { text-align: center; margin-bottom: 30px; }
.hero h1 { font-size: 2.2rem; margin-bottom: 10px; }
.hero p { color: var(--text-muted); }

/* Calculator Page Premium UI */
.calc-box {
    max-width: 550px;
    margin: 0 auto;
    background: var(--card-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    padding: 40px;
    border-radius: 24px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}
.input-group { margin-bottom: 20px; }
.input-label { display: block; margin-bottom: 8px; font-weight: 600; color: var(--text-muted); font-size: 0.9rem; }
.premium-input {
    width: 100%; padding: 16px 20px; font-size: 1rem;
    border: 1px solid var(--border-color); border-radius: 12px;
    background: rgba(255,255,255,0.4); color: var(--text-main);
    outline: none; transition: all 0.3s ease;
}
.dark-mode .premium-input { background: rgba(255,255,255,0.05); }
.premium-input:focus { border-color: var(--primary); box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1); }
.premium-btn {
    width: 100%; padding: 18px; font-size: 1.1rem; font-weight: 600;
    color: white; background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border: none; border-radius: 12px; cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s; box-shadow: 0 4px 15px rgba(99, 102, 241, 0.3);
}
.premium-btn:active { transform: scale(0.97); }
.result-box {
    margin-top: 25px; padding: 25px; border-radius: 12px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.1));
    text-align: center; color: var(--text-main); font-size: 1.1rem;
    display: none; border: 1px solid rgba(99, 102, 241, 0.2);
}
.result-box span { font-weight: 700; color: var(--primary); display: block; margin-top: 5px; }
.back-link { display: block; text-align: center; margin-top: 30px; color: var(--text-muted); text-decoration: none; font-weight: 500; }
.back-link:hover { color: var(--primary); }
.info-section{margin-top:25px;background:var(--card-bg);border:1px solid var(--border-color);padding:22px 26px;border-radius:16px;box-shadow:var(--shadow)}.info-section h2{font-size:1.25rem;margin-bottom:10px;color:var(--primary)}.info-section p{color:var(--text-muted);line-height:1.65;margin-bottom:8px;font-size:.95rem}.info-section .formula{background:rgba(99,102,241,0.1);padding:10px 14px;border-radius:8px;font-family:monospace;font-size:.92rem;margin:8px 0;overflow-x:auto;color:var(--text-main)}.dark-mode .info-section .formula{background:rgba(99,102,241,0.18)}