:root {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --accent: #3b82f6;
    --accent-hover: #2563eb;
    --success: #10b981;
    --danger: #ef4444;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', sans-serif;
}

body {
    background: linear-gradient(135deg, var(--bg-primary), #020617);
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: rgba(30, 41, 59, 0.7);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 24px;
    padding: 40px;
    width: 100%;
    max-width: 600px;
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
}

header {
    text-align: center;
    margin-bottom: 30px;
}

header h1 {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 8px;
    background: linear-gradient(to right, #60a5fa, #a78bfa);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

header p {
    color: var(--text-muted);
    font-size: 14px;
}

.input-group {
    margin-bottom: 20px;
}

label {
    display: block;
    margin-bottom: 8px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-muted);
}

select, input {
    width: 100%;
    padding: 14px 16px;
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 12px;
    color: var(--text-main);
    font-size: 16px;
    outline: none;
    transition: all 0.3s ease;
}

select:focus, input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.2);
}

button {
    width: 100%;
    padding: 16px;
    background: var(--accent);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.3s ease, transform 0.1s ease;
    margin-top: 10px;
}

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

button:active {
    transform: scale(0.98);
}

.results-container {
    margin-top: 30px;
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    justify-content: space-between;
    animation: fadeIn 0.4s ease-out forwards;
}

.hidden {
    display: none;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.result-card {
    flex: 1;
    min-width: 150px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(255, 255, 255, 0.05);
    padding: 20px;
    border-radius: 16px;
    text-align: center;
}

.result-card h3 {
    font-size: 14px;
    color: var(--text-muted);
    margin-bottom: 5px;
}

.result-card .rate {
    font-size: 12px;
    margin-bottom: 10px;
}

.result-card .amount {
    font-size: 20px;
    font-weight: 700;
}

.filer .amount { color: var(--success); }
.non-filer .amount { color: var(--danger); }

.vs {
    display: flex;
    align-items: center;
    font-weight: 700;
    color: var(--text-muted);
}

.savings-card {
    width: 100%;
    margin-top: 15px;
    background: linear-gradient(135deg, rgba(16, 185, 129, 0.1), rgba(16, 185, 129, 0.05));
    border: 1px solid rgba(16, 185, 129, 0.2);
    border-radius: 16px;
    padding: 20px;
    text-align: center;
}

.savings-card h3 {
    font-size: 16px;
    color: var(--success);
    margin-bottom: 8px;
}

.savings-amount {
    font-size: 28px;
    font-weight: 700;
    color: var(--success);
}