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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #e9ecef 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    color: #2c3e50;
}

.container {
    background: #ffffff;
    border-radius: 16px;
    box-shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
    padding: 48px;
    max-width: 860px;
    width: 100%;
    text-align: center;
    border: 1px solid rgba(0, 0, 0, 0.06);
}

h1 {
    color: #1a202c;
    margin-bottom: 24px;
    font-size: 2em;
    font-weight: 600;
    letter-spacing: -0.02em;
}

.welcome-message {
    color: #4a5568;
    font-size: 1.2em;
    margin-bottom: 20px;
}

.welcome-message h2 {
    color: #2d3748;
    font-weight: 600;
    margin-bottom: 12px;
    font-size: 1.8em;
}

.message {
    padding: 18px 24px;
    border-radius: 10px;
    margin: 24px 0;
    font-size: 1.05em;
    line-height: 1.6;
}

.success {
    background-color: #f0fdf4;
    border: 1.5px solid #86efac;
    color: #166534;
}

.success strong {
    color: #15803d;
}

.error {
    background-color: #fef2f2;
    border: 1.5px solid #fca5a5;
    color: #991b1b;
}

.error strong {
    color: #dc2626;
}

.info {
    background-color: #eff6ff;
    border: 1.5px solid #93c5fd;
    color: #1e40af;
}

.info strong {
    color: #1d4ed8;
}

.btn {
    background: linear-gradient(135deg, #3b82f6 0%, #2563eb 100%);
    color: white;
    border: none;
    padding: 14px 32px;
    font-size: 1em;
    font-weight: 500;
    border-radius: 8px;
    cursor: pointer;
    text-decoration: none;
    display: inline-block;
    margin-top: 16px;
    transition: all 0.2s ease;
    box-shadow: 0 2px 8px rgba(59, 130, 246, 0.25);
}

.btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 16px rgba(59, 130, 246, 0.35);
    background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
}

.btn:active {
    transform: translateY(0);
    box-shadow: 0 2px 8px rgba(59, 130, 246, 0.25);
}

/* Loading Spinner */
.loader-container {
    display: none;
    margin: 24px 0;
}

.loader-container.active {
    display: block;
}

.loader {
    border: 4px solid #e5e7eb;
    border-top: 4px solid #3b82f6;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 0.8s linear infinite;
    margin: 0 auto;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.loading-text {
    color: #3b82f6;
    margin-top: 12px;
    font-weight: 500;
    font-size: 0.95em;
}

.hidden {
    display: none;
}

a {
    color: #3b82f6;
    text-decoration: none;
    font-weight: 500;
}

a:hover {
    color: #2563eb;
    text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 640px) {
    .container {
        padding: 32px 24px;
    }

    h1 {
        font-size: 1.75em;
    }

    .welcome-message h2 {
        font-size: 1.5em;
    }
}

/* ============================================================
   Logged-in welcome area
   ============================================================ */
.logged-in-text {
    margin-top: 10px;
    color: #718096;
    font-size: 1.05em;
}

/* ============================================================
   OS Tab Bar
   ============================================================ */
.os-tab-container {
    margin-top: 28px;
    border: 1.5px solid #e2e8f0;
    border-radius: 12px;
    overflow: hidden;
    text-align: left;
}

.os-tab-bar {
    display: flex;
    background: #f7f8fa;
    border-bottom: 1.5px solid #e2e8f0;
}

.os-tab-btn {
    flex: 1;
    padding: 14px 10px;
    font-size: 0.97em;
    font-weight: 600;
    color: #4a5568;
    background: transparent;
    border: none;
    border-right: 1.5px solid #e2e8f0;
    cursor: pointer;
    transition: background 0.15s, color 0.15s;
    letter-spacing: 0.01em;
}

.os-tab-btn:last-child {
    border-right: none;
}

.os-tab-btn:hover {
    background: #edf2f7;
    color: #2563eb;
}

.os-tab-btn.active {
    background: #ffffff;
    color: #2563eb;
    border-bottom: 3px solid #2563eb;
    margin-bottom: -1.5px;
}

/* ============================================================
   OS Tab Panels
   ============================================================ */
.os-tab-panel {
    display: none;
    padding: 28px 32px 24px 32px;
    background: #ffffff;
}

.os-tab-panel.active {
    display: block;
}

/* ============================================================
   Instructions intro text
   ============================================================ */
.instructions-intro {
    font-size: 1em;
    color: #4a5568;
    margin-bottom: 24px;
    line-height: 1.65;
    padding: 14px 18px;
    background: #eff6ff;
    border-left: 4px solid #3b82f6;
    border-radius: 6px;
}

/* ============================================================
   Step blocks
   ============================================================ */
.os-instructions {
    display: flex;
    flex-direction: column;
    gap: 0;
}

.step {
    display: flex;
    align-items: flex-start;
    gap: 16px;
    padding: 20px 0;
    border-bottom: 1px solid #f0f4f8;
}

.step:last-child {
    border-bottom: none;
}

.step-number {
    flex-shrink: 0;
    width: 34px;
    height: 34px;
    border-radius: 50%;
    background: linear-gradient(135deg, #3b82f6 0%, #2563eb 100%);
    color: #ffffff;
    font-size: 0.95em;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-top: 2px;
    box-shadow: 0 2px 6px rgba(59, 130, 246, 0.3);
}

.step-content {
    flex: 1;
    font-size: 0.97em;
    color: #2d3748;
    line-height: 1.65;
}

.step-content strong {
    display: block;
    font-size: 1em;
    font-weight: 600;
    color: #1a202c;
    margin-bottom: 5px;
}

.step-content p {
    color: #4a5568;
    margin-top: 4px;
}

.step-content em {
    font-style: normal;
    font-weight: 600;
    color: #2563eb;
}

/* ============================================================
   Inline screenshots
   ============================================================ */
.screenshot-container {
    margin-top: 14px;
    text-align: center;
}

.step-screenshot {
    max-width: 100%;
    width: 480px;
    border-radius: 10px;
    border: 1.5px solid #e2e8f0;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.10);
    display: block;
    margin: 0 auto;
}

.screenshot-caption {
    margin-top: 8px;
    font-size: 0.85em;
    color: #718096;
    font-style: italic;
}

/* ============================================================
   Screenshot placeholder (for Linux / Windows)
   ============================================================ */
.screenshot-placeholder {
    margin-top: 12px;
    padding: 12px 16px;
    background: #f7f8fa;
    border: 1.5px dashed #cbd5e0;
    border-radius: 8px;
    color: #a0aec0;
    font-size: 0.88em;
    text-align: center;
    font-style: italic;
}

/* ============================================================
   Register button row inside each tab
   ============================================================ */
.tab-register-btn-row {
    margin-top: 28px;
    padding-top: 22px;
    border-top: 1.5px solid #e2e8f0;
    text-align: center;
}

.register-btn {
    font-size: 1.05em;
    padding: 15px 44px;
    letter-spacing: 0.01em;
}

/* ============================================================
   Bottom actions (logout + support)
   ============================================================ */
.bottom-actions {
    margin-top: 28px;
    text-align: center;
}

.btn-logout {
    background: linear-gradient(135deg, #e53e3e 0%, #c53030 100%);
    box-shadow: 0 2px 8px rgba(229, 62, 62, 0.25);
}

.btn-logout:hover {
    background: linear-gradient(135deg, #c53030 0%, #9b2c2c 100%);
    box-shadow: 0 4px 16px rgba(229, 62, 62, 0.35);
}

.support-text {
    margin-top: 18px;
    color: #718096;
    font-size: 0.95rem;
}

.support-text a {
    color: #4a5568;
    font-weight: 600;
    white-space: nowrap;
}

/* ============================================================
   Responsive adjustments for tabs
   ============================================================ */
@media (max-width: 640px) {
    .os-tab-panel {
        padding: 20px 16px 18px 16px;
    }

    .os-tab-btn {
        font-size: 0.85em;
        padding: 12px 6px;
    }

    .step {
        gap: 12px;
    }

    .step-number {
        width: 28px;
        height: 28px;
        font-size: 0.85em;
    }

    .step-screenshot {
        width: 100%;
    }

    .register-btn {
        padding: 14px 28px;
        font-size: 1em;
    }
}