/* RESET / BASE */
*,
*::before,
*::after {
    box-sizing: border-box;
}

html, body {
    margin: 0;
    padding: 0;
}

body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    color: #111;
    background-color: #050505;
}

/* LAYOUT SHELL */
.page-shell {
    min-height: 100vh;
    display: grid;
    grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr);
    background: radial-gradient(circle at top left, #1c1c1c 0, #050505 50%, #000 100%);
    color: #fff;
}

/* BRAND SIDE */
.brand-side {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px;
}

.brand-inner {
    max-width: 420px;
}

.brand-mark {
    width: 52px;
    height: 52px;
    border-radius: 50%;
    border: 1px solid #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 18px;
    margin-bottom: 16px;
}

.brand-title {
    font-size: 32px;
    letter-spacing: 0.06em;
    text-transform: uppercase;
    margin-bottom: 10px;
}

.brand-subtitle {
    color: #c4c4c4;
    font-size: 15px;
    max-width: 280px;
}

/* AUTH SIDE */
.auth-side {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.auth-card {
    width: 100%;
    max-width: 420px;
    background: #ffffff;
    color: #111;
    border-radius: 24px;
    padding: 28px 26px 26px;
    box-shadow:
        0 26px 60px rgba(0, 0, 0, 0.5),
        0 0 0 1px rgba(0, 0, 0, 0.08);
}

.auth-header {
    margin-bottom: 20px;
}

.auth-title {
    font-size: 24px;
    margin: 0 0 4px;
}

.auth-caption {
    margin: 0;
    font-size: 14px;
    color: #555;
}

/* ALERT */
.alert {
    margin-bottom: 18px;
    padding: 10px 12px;
    border-radius: 10px;
    background: #fdf2f2;
    color: #b91c1c;
    border: 1px solid #fecaca;
    font-size: 13px;
}

/* ROLE TABS */
.role-tabs {
    position: relative;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    border-radius: 999px;
    padding: 3px;
    background: #f3f3f3;
    margin-bottom: 22px;
}

.role-input {
    display: none;
}

.role-tab {
    position: relative;
    z-index: 1;
    cursor: pointer;
    text-align: center;
    padding: 8px 0;
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: #555;
    user-select: none;
    transition: color 0.2s ease-out;
}

.role-label {
    display: inline-block;
}

.role-active-indicator {
    position: absolute;
    top: 3px;
    bottom: 3px;
    width: calc(33.333% - 4px);
    border-radius: 999px;
    background: #111;
    transition: transform 0.25s ease-out;
}

/* TAB LOGIC */
#tab-student:checked ~ .role-tab[for="tab-student"],
#tab-teacher:checked ~ .role-tab[for="tab-teacher"],
#tab-admin:checked  ~ .role-tab[for="tab-admin"] {
    color: #fff;
}

#tab-student:checked ~ .role-active-indicator {
    transform: translateX(0%);
}

#tab-teacher:checked ~ .role-active-indicator {
    transform: translateX(100%);
}

#tab-admin:checked ~ .role-active-indicator {
    transform: translateX(200%);
}

/* FORM FIELDS */
.auth-form {
    display: flex;
    flex-direction: column;
}

.field-group {
    margin-bottom: 16px;
}

.field-label {
    display: block;
    font-size: 13px;
    font-weight: 500;
    margin-bottom: 6px;
    color: #333;
}

.field-input {
    width: 100%;
    border-radius: 12px;
    border: 1px solid #d4d4d4;
    padding: 11px 13px;
    font-size: 15px;
    background: #f9fafb;
    transition: border-color 0.18s ease-out, box-shadow 0.18s ease-out, background 0.18s ease-out;
}

.field-input:focus {
    outline: none;
    border-color: #111;
    background: #fff;
    box-shadow: 0 0 0 3px rgba(0, 0, 0, 0.08);
}

.field-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 18px;
    gap: 12px;
}

.checkbox {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 13px;
    color: #444;
    cursor: pointer;
}

.checkbox input {
    width: 14px;
    height: 14px;
}

/* BUTTON */
.btn-primary {
    border: none;
    border-radius: 999px;
    padding: 11px 16px;
    background: #111;
    color: #fff;
    font-weight: 600;
    font-size: 15px;
    cursor: pointer;
    width: 100%;
    margin-bottom: 12px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    transition: background 0.18s ease-out, transform 0.1s ease-out, box-shadow 0.18s ease-out;
}

.btn-primary:hover {
    background: #222;
    transform: translateY(-1px);
    box-shadow: 0 14px 30px rgba(0, 0, 0, 0.4);
}

.btn-primary:active {
    transform: translateY(0);
    box-shadow: none;
}

/* LINKS / TEXT */
.link-muted {
    font-size: 13px;
    color: #666;
    text-decoration: none;
    border-bottom: 1px solid transparent;
    padding-bottom: 1px;
    transition: color 0.15s ease-out, border-color 0.15s ease-out;
}

.link-muted:hover {
    color: #111;
    border-color: #111;
}

.legal-text {
    font-size: 11px;
    color: #777;
    margin: 0;
    text-align: center;
}

/* RESPONSIVE */
@media (max-width: 900px) {
    .page-shell {
        grid-template-columns: 1fr;
        padding: 16px;
    }

    .brand-side {
        display: none;
    }

    .auth-side {
        padding: 0;
    }

    .auth-card {
        max-width: 480px;
        margin: 0 auto;
    }
}

@media (max-width: 480px) {
    .auth-card {
        border-radius: 18px;
        padding: 22px 18px 18px;
    }

    .auth-title {
        font-size: 21px;
    }
}