* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background: linear-gradient(135deg, #0f172a 0%, #1e1b4b 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    color: #fff;
}

.converter-box {
    background: rgba(30, 41, 59, 0.7);
    padding: 30px;
    border-radius: 20px;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    width: 100%;
    max-width: 450px;
    text-align: center;
}

h2 {
    font-size: 28px;
    margin-bottom: 5px;
    background: linear-gradient(to right, #38bdf8, #818cf8);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.subtitle {
    color: #94a3b8;
    font-size: 14px;
    margin-bottom: 25px;
}

.input-group, .select-box {
    text-align: left;
    margin-bottom: 20px;
}

label {
    display: block;
    color: #94a3b8;
    font-size: 12px;
    margin-bottom: 5px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

input, select {
    width: 100%;
    padding: 12px;
    background: #0f172a;
    border: 1px solid #334155;
    border-radius: 10px;
    color: #fff;
    font-size: 16px;
    outline: none;
    transition: 0.3s;
}

input:focus, select:focus {
    border-color: #6366f1;
    box-shadow: 0 0 10px rgba(99, 102, 241, 0.3);
}

.selection-group {
    display: flex;
    align-items: center;
    gap: 15px;
}

.select-box {
    flex: 1;
}

.swap-btn {
    background: #334155;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    margin-top: 5px;
    font-size: 20px;
    transition: 0.3s;
    user-select: none;
}

.swap-btn:hover {
    background: #6366f1;
    transform: rotate(180deg);
}

.result-box {
    background: #0f172a;
    padding: 20px;
    border-radius: 12px;
    margin: 25px 0;
    border: 1px dashed #334155;
}

#resultText {
    font-size: 22px;
    font-weight: bold;
    color: #4ade80;
}

button {
    width: 100%;
    padding: 15px;
    background: linear-gradient(135deg, #6366f1 0%, #4f46e5 100%);
    border: none;
    border-radius: 12px;
    color: #fff;
    font-size: 16px;
    font-weight: bold;
    cursor: pointer;
    transition: 0.3s;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.6);
}