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

:root {
    --primary-color: #2563eb;
    --primary-dark: #1d4ed8;
    --primary-light: #3b82f6;
    --secondary-color: #64748b;
    --background-color: #f1f5f9;
    --white: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    overflow: hidden;
    height: 100vh;
}

.hidden {
    display: none !important;
}

/* Login Screen */
.login-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.login-container {
    background: var(--white);
    padding: 3rem;
    border-radius: 20px;
    box-shadow: var(--shadow-lg);
    text-align: center;
    max-width: 400px;
    width: 90%;
}

.logo {
    margin-bottom: 1.5rem;
}

.logo i {
    font-size: 4rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.logo h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
}

.tagline {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 1rem;
}

.sign-in-btn {
    width: 100%;
    padding: 1rem 2rem;
    background: var(--white);
    border: 2px solid var(--border-color);
    border-radius: 12px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    transition: all 0.3s ease;
}

.sign-in-btn:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.sign-in-btn img {
    width: 24px;
    height: 24px;
}

/* Main App Layout */
.main-app {
    display: flex;
    height: 100vh;
    background: var(--white);
}

/* Sidebar */
.sidebar {
    width: 350px;
    background: var(--white);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
}

.sidebar-header {
    padding: 1.5rem;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: var(--white);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.user-profile {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.avatar {
    width: 45px;
    height: 45px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid rgba(255, 255, 255, 0.3);
}

.user-profile span {
    font-weight: 600;
    font-size: 1.1rem;
}

.header-actions {
    display: flex;
    gap: 0.5rem;
}

.icon-btn {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    color: var(--white);
    width: 40px;
    height: 40px;
    border-radius: 10px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
}

.icon-btn:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: scale(1.05);
}

.icon-btn.danger {
    background: rgba(239, 68, 68, 0.2);
    color: var(--danger-color);
}

.icon-btn.danger:hover {
    background: rgba(239, 68, 68, 0.3);
}

.search-box {
    padding: 1rem 1.5rem;
    position: relative;
}

.search-box i {
    position: absolute;
    left: 2.5rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
}

.search-box input {
    width: 100%;
    padding: 0.75rem 1rem 0.75rem 2.5rem;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    font-size: 0.95rem;
    outline: none;
    transition: all 0.3s ease;
}

.search-box input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.contacts-list {
    flex: 1;
    overflow-y: auto;
    padding: 0.5rem;
}

.contact-item {
    padding: 1rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    cursor: pointer;
    border-radius: 12px;
    transition: all 0.2s ease;
    margin-bottom: 0.5rem;
}

.contact-item:hover {
    background: var(--background-color);
}

.contact-item.active {
    background: rgba(37, 99, 235, 0.1);
    border-left: 3px solid var(--primary-color);
}

.contact-avatar {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary-color) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    font-weight: 600;
    font-size: 1.2rem;
    flex-shrink: 0;
}

.contact-info {
    flex: 1;
    overflow: hidden;
}

.contact-name {
    font-weight: 600;
    margin-bottom: 0.25rem;
    color: var(--text-primary);
}

.contact-last-message {
    font-size: 0.85rem;
    color: var(--text-secondary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.contact-time {
    font-size: 0.75rem;
    color: var(--text-secondary);
    flex-shrink: 0;
}

.unread-badge {
    background: var(--primary-color);
    color: var(--white);
    border-radius: 50%;
    width: 22px;
    height: 22px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    margin-top: 0.25rem;
}

/* Chat Area */
.chat-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--background-color);
}

.empty-state {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
}

.empty-state i {
    font-size: 5rem;
    margin-bottom: 1.5rem;
    opacity: 0.3;
}

.empty-state h2 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.empty-state p {
    font-size: 1rem;
}

.chat-container {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.chat-header {
    padding: 1rem 1.5rem;
    background: var(--white);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.chat-user-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.avatar-small {
    width: 45px;
    height: 45px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--primary-color) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    font-weight: 600;
    font-size: 1.1rem;
}

.chat-user-details h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.chat-user-details span {
    font-size: 0.85rem;
    color: var(--success-color);
}

.messages-container {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.message {
    max-width: 70%;
    padding: 0.75rem 1rem;
    border-radius: 15px;
    position: relative;
    animation: slideIn 0.3s ease;
}

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

.message.sent {
    align-self: flex-end;
    background: var(--primary-color);
    color: var(--white);
    border-bottom-right-radius: 5px;
}

.message.received {
    align-self: flex-start;
    background: var(--white);
    color: var(--text-primary);
    border-bottom-left-radius: 5px;
    box-shadow: var(--shadow-sm);
}

.message-text {
    word-wrap: break-word;
    line-height: 1.4;
}

.message-time {
    font-size: 0.7rem;
    opacity: 0.7;
    margin-top: 0.25rem;
    text-align: right;
}

.message-input-area {
    padding: 1rem 1.5rem;
    background: var(--white);
    border-top: 1px solid var(--border-color);
}

.input-wrapper {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.input-wrapper input {
    flex: 1;
    padding: 0.9rem 1.2rem;
    border: 1px solid var(--border-color);
    border-radius: 25px;
    font-size: 0.95rem;
    outline: none;
    transition: all 0.3s ease;
}

.input-wrapper input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.send-btn {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: var(--primary-color);
    border: none;
    color: var(--white);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    transition: all 0.3s ease;
}

.send-btn:hover {
    background: var(--primary-dark);
    transform: scale(1.05);
}

.send-btn:active {
    transform: scale(0.95);
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
    backdrop-filter: blur(5px);
}

.modal-content {
    background: var(--white);
    border-radius: 20px;
    width: 90%;
    max-width: 450px;
    box-shadow: var(--shadow-lg);
    animation: modalSlideIn 0.3s ease;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h2 {
    font-size: 1.3rem;
    font-weight: 600;
}

.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-secondary);
    cursor: pointer;
    width: 35px;
    height: 35px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.close-btn:hover {
    background: var(--background-color);
    color: var(--text-primary);
}

.modal-body {
    padding: 1.5rem;
}

.modal-body label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.modal-body input {
    width: 100%;
    padding: 0.9rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 10px;
    font-size: 1rem;
    outline: none;
    transition: all 0.3s ease;
}

.modal-body input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.hint {
    margin-top: 0.75rem;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.modal-footer {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border-color);
    display: flex;
    gap: 1rem;
    justify-content: flex-end;
}

.btn-primary, .btn-secondary {
    padding: 0.75rem 1.5rem;
    border-radius: 10px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    border: none;
}

.btn-primary {
    background: var(--primary-color);
    color: var(--white);
}

.btn-primary:hover {
    background: var(--primary-dark);
}

.btn-secondary {
    background: var(--background-color);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--border-color);
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--secondary-color);
}

/* Responsive */
@media (max-width: 768px) {
    .sidebar {
        width: 100%;
        position: absolute;
        z-index: 100;
        transform: translateX(-100%);
        transition: transform 0.3s ease;
    }

    .sidebar.show {
        transform: translateX(0);
    }

    .chat-area {
        width: 100%;
    }

    .message {
        max-width: 85%;
    }
}

/* Loading Animation */
.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
    border-top-color: var(--white);
    animation: spin 1s ease-in-out infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}