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

body {
    background-color: rgba(0, 0, 0, 0.8);
    font-family: sans-serif;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow: hidden;
}

/* Κουμπί Επιστροφής */
.btn-back-home {
    position: absolute;
    top: 30px;
    left: 40px;
    display: flex;
    align-items: center;
    gap: 8px;
    text-decoration: none;
    color: rgba(255, 255, 255, 0.4);
    font-size: 15px;
    font-weight: 100;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: all 0.3s ease;
}

.btn-back-home:hover {
    color: #4CAF50;
    transform: translateX(-4px);
}

/* Container και Κάρτα */
.auth-wrapper {
    width: 100%;
    max-width: 440px;
    padding: 20px;
}

.auth-card {
    background-color: rgba(0, 0, 0, 0.4);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: 8px;
    padding: 40px 30px;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.5);
    position: relative;
}

/* Σχεδιασμός των Tabs */
.auth-tabs {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-bottom: 35px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    padding-bottom: 15px;
}

.tab-label {
    font-size: 22px;
    font-weight: 100;
    color: rgba(255, 255, 255, 0.2);
    text-transform: uppercase;
    letter-spacing: 1px;
    cursor: pointer;
    transition: all 0.3s ease;
    padding-bottom: 5px;
    position: relative;
}

/* Ήπιο Hover στα Tabs */
.tab-label:hover {
    color: rgba(255, 255, 255, 0.6);
}

/* ==================== Η ΜΑΓΕΙΑ ΤΗΣ ΕΝΑΛΛΑΓΗΣ (CSS LOGIC) ==================== */

/* Αρχικά κρύβουμε και τις δύο φόρμες */
.auth-form {
    display: none;
    animation: fadeInForm 0.4s ease-in-out forwards;
}

/* Όταν είναι επιλεγμένο το Sign In radio button */
#tab-signin:checked ~ .auth-wrapper .form-signin {
    display: block;
}
#tab-signin:checked ~ .auth-wrapper .label-signin {
    color: #4CAF50; /* Το επιλεγμένο tab γίνεται πράσινο */
    font-weight: bold;
}

/* Όταν είναι επιλεγμένο το Sign Up radio button */
#tab-signup:checked ~ .auth-wrapper .form-signup {
    display: block;
}
#tab-signup:checked ~ .auth-wrapper .label-signup {
    color: #4CAF50;
    font-weight: bold;
}

/* ============================================================================ */

/* Στυλ Πεδίων Εισαγωγής */
.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 22px;
}

.input-group label {
    font-size: 13px;
    color: rgba(255, 255, 255, 0.5);
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.input-group input, .select-role {
    background-color: rgba(255, 255, 255, 0.04);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 4px;
    padding: 12px 16px;
    color: #ffffff;
    font-size: 15px;
    outline: none;
    transition: all 0.3s ease;
}

.input-group input:focus, .select-role:focus {
    border-color: #4CAF50;
    background-color: rgba(255, 255, 255, 0.08);
    box-shadow: 0 0 10px rgba(76, 175, 80, 0.15);
}

.select-role option {
    background-color: #1a1a1a;
    color: #ffffff;
}

/* Στυλ Κουμπιών */
.btn-auth-submit {
    width: 100%;
    background-color: #4CAF50;
    color: #ffffff;
    border: none;
    font-size: 16px;
    font-weight: bold;
    padding: 14px;
    border-radius: 4px;
    cursor: pointer;
    box-shadow: 0 4px 15px rgba(76, 175, 80, 0.2);
    transition: all 0.3s ease;
    margin-top: 10px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.btn-auth-submit:hover {
    background-color: #45a049;
    box-shadow: 0 6px 20px rgba(76, 175, 80, 0.4);
    transform: translateY(-2px);
}

.auth-forgot {
    margin-top: 20px;
    text-align: center;
}

.auth-forgot a {
    font-size: 13px;
    color: #666666;
    text-decoration: none;
    transition: color 0.2s ease;
}

.auth-forgot a:hover {
    color: rgba(255, 255, 255, 0.6);
    text-decoration: underline;
}

/* Animation για smooth εμφάνιση */
@keyframes fadeInForm {
    from {
        opacity: 0;
        transform: translateY(8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@media (max-width: 600px) {
    .btn-back-home {
        top: 20px;
        left: 20px;
        font-size: 13px;
    }
}