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

:root {
    --bg-top: #10233f;
    --bg-bottom: #17345c;
    --bg-accent: #53b7ff;
    --surface: rgba(248, 250, 252, 0.9);
    --surface-strong: rgba(255, 255, 255, 0.98);
    --surface-soft: rgba(255, 255, 255, 0.72);
    --surface-dark: #10233f;
    --line: rgba(16, 35, 63, 0.08);
    --line-strong: rgba(16, 35, 63, 0.16);
    --text: #13233b;
    --text-muted: #58708f;
    --text-soft: #8ea2bd;
    --primary: #2a9df4;
    --primary-strong: #1976d2;
    --primary-soft: #d9efff;
    --secondary: #4ec5ff;
    --secondary-strong: #1d9ee6;
    --danger: #dc2626;
    --danger-soft: #fef2f2;
    --success: #15803d;
    --success-soft: #f0fdf4;
    --shadow-lg: 0 30px 80px rgba(15, 23, 42, 0.18);
    --shadow-md: 0 18px 45px rgba(15, 23, 42, 0.14);
    --shadow-sm: 0 10px 24px rgba(15, 23, 42, 0.08);
    --radius-xl: 28px;
    --radius-lg: 20px;
    --radius-md: 16px;
    --radius-sm: 12px;
}

html {
    color-scheme: light;
}

body {
    font-family: "Segoe UI", "Trebuchet MS", "Helvetica Neue", sans-serif;
    background:
        radial-gradient(circle at top left, rgba(78, 197, 255, 0.22), transparent 28%),
        radial-gradient(circle at top right, rgba(42, 157, 244, 0.18), transparent 24%),
        linear-gradient(145deg, var(--bg-top) 0%, var(--bg-bottom) 55%, #345b8a 100%);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.5;
    position: relative;
}

body::before {
    content: "";
    position: fixed;
    inset: 0;
    pointer-events: none;
    background:
        linear-gradient(rgba(255, 255, 255, 0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
    background-size: 32px 32px;
    mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 0.35), transparent 78%);
}

a {
    color: inherit;
}

button,
input,
textarea {
    font: inherit;
}

button {
    transition:
        transform 0.24s ease,
        box-shadow 0.24s ease,
        background-color 0.24s ease,
        border-color 0.24s ease,
        color 0.24s ease;
}

button:hover {
    transform: translateY(-1px);
}

button:active {
    transform: translateY(0);
}

button:focus-visible,
input:focus-visible,
textarea:focus-visible,
a:focus-visible {
    outline: 3px solid rgba(42, 157, 244, 0.22);
    outline-offset: 2px;
}

/* Auth Pages */
.auth-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 32px 20px;
    position: relative;
}

.auth-container::before,
.auth-container::after {
    content: "";
    position: fixed;
    border-radius: 999px;
    filter: blur(18px);
    opacity: 0.7;
    pointer-events: none;
}

.auth-container::before {
    width: 240px;
    height: 240px;
    top: 9vh;
    left: 8vw;
    background: rgba(78, 197, 255, 0.28);
}

.auth-container::after {
    width: 300px;
    height: 300px;
    right: 6vw;
    bottom: 6vh;
    background: rgba(42, 157, 244, 0.2);
}

.auth-card {
    width: 100%;
    max-width: 430px;
    padding: 40px 36px 34px;
    border-radius: var(--radius-xl);
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(248, 250, 252, 0.94));
    border: 1px solid rgba(255, 255, 255, 0.58);
    box-shadow: var(--shadow-lg);
    backdrop-filter: blur(18px);
    animation: slideUp 0.55s cubic-bezier(0.2, 0.8, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.auth-card::before {
    content: "";
    position: absolute;
    inset: 0 0 auto;
    height: 6px;
    background: linear-gradient(90deg, #80d8ff 0%, var(--secondary) 35%, var(--primary) 100%);
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(26px) scale(0.985);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

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

.auth-card h2 {
    margin-bottom: 10px;
    color: var(--text);
    font-size: clamp(2rem, 4vw, 2.4rem);
    line-height: 1.05;
    letter-spacing: -0.04em;
}

.auth-card h2 + .error-message,
.auth-card h2 + .success-message,
.auth-card h2 + form,
.auth-card h2 + div {
    margin-top: 22px;
}

.form-group {
    margin-bottom: 18px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    color: var(--text-muted);
    font-size: 0.95rem;
    font-weight: 700;
    letter-spacing: 0.01em;
}

.form-group input,
.create-chat-form input,
.add-user-container input,
.message-input-area textarea {
    width: 100%;
    border: 1px solid rgba(148, 163, 184, 0.28);
    border-radius: 15px;
    padding: 14px 16px;
    background: rgba(255, 255, 255, 0.92);
    color: var(--text);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.75);
    transition:
        border-color 0.24s ease,
        box-shadow 0.24s ease,
        background-color 0.24s ease;
}

.form-group input::placeholder,
.create-chat-form input::placeholder,
.add-user-container input::placeholder,
.message-input-area textarea::placeholder {
    color: #94a3b8;
}

.form-group input:focus,
.create-chat-form input:focus,
.add-user-container input:focus,
.message-input-area textarea:focus {
    outline: none;
    border-color: rgba(42, 157, 244, 0.5);
    box-shadow:
        0 0 0 4px rgba(42, 157, 244, 0.12),
        0 10px 22px rgba(25, 118, 210, 0.08);
    background: #ffffff;
}

.btn {
    width: 100%;
    padding: 14px 18px;
    border: 0;
    border-radius: 16px;
    font-size: 1rem;
    font-weight: 800;
    letter-spacing: 0.01em;
    cursor: pointer;
}

.btn-primary,
.btn-send,
.btn-add-user,
.create-chat-form button,
.add-user-container button,
.no-chat-selected button,
.modal-content button,
.btn-icon {
    background: linear-gradient(135deg, #73d4ff 0%, var(--secondary) 30%, var(--primary) 100%);
    color: #ffffff;
    box-shadow: 0 16px 32px rgba(25, 118, 210, 0.2);
}

.btn-primary:hover,
.btn-send:hover,
.btn-add-user:hover,
.create-chat-form button:hover,
.add-user-container button:hover,
.no-chat-selected button:hover,
.modal-content button:hover,
.btn-icon:hover {
    box-shadow: 0 18px 36px rgba(25, 118, 210, 0.26);
}

.auth-link {
    margin-top: 22px;
    color: var(--text-muted);
    text-align: center;
    font-size: 0.96rem;
}

.auth-link a {
    color: var(--primary-strong);
    font-weight: 800;
    text-decoration: none;
}

.auth-link a:hover {
    color: var(--secondary-strong);
}

.btn-loading {
    position: relative;
    color: rgba(255, 255, 255, 0.92);
    pointer-events: none;
}

.btn-loading::after {
    content: "";
    display: inline-block;
    width: 14px;
    height: 14px;
    margin-left: 10px;
    border: 2px solid rgba(255, 255, 255, 0.35);
    border-top-color: #ffffff;
    border-radius: 50%;
    vertical-align: -2px;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

.btn:disabled,
.btn-icon:disabled,
.btn-send:disabled,
.btn-add-user:disabled {
    cursor: wait;
    filter: saturate(0.8);
    opacity: 0.88;
    transform: none;
}

.loading-message {
    display: none;
    margin-bottom: 18px;
    padding: 12px 14px;
    border-radius: 14px;
    background: rgba(217, 239, 255, 0.95);
    color: var(--primary-strong);
    border: 1px solid rgba(42, 157, 244, 0.16);
    font-size: 0.92rem;
    font-weight: 700;
}

.error-message,
.success-message {
    margin-bottom: 18px;
    padding: 12px 14px;
    border-radius: 14px;
    font-size: 0.92rem;
    font-weight: 600;
}

.error-message {
    background: var(--danger-soft);
    color: #b91c1c;
    border: 1px solid rgba(220, 38, 38, 0.14);
}

.success-message {
    background: var(--success-soft);
    color: var(--success);
    border: 1px solid rgba(21, 128, 61, 0.12);
}

/* Chat Room */
.chat-room {
    display: flex;
    min-height: 100vh;
    padding: 18px;
    gap: 18px;
    position: relative;
}

.sidebar,
.chat-area {
    background: var(--surface);
    backdrop-filter: blur(18px);
    border: 1px solid rgba(255, 255, 255, 0.5);
    box-shadow: var(--shadow-md);
}

/* Sidebar */
.sidebar {
    width: 320px;
    display: flex;
    flex-direction: column;
    border-radius: 30px;
    overflow: hidden;
}

.sidebar-header,
.chat-header {
    position: relative;
}

.sidebar-header {
    padding: 24px 24px 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--line);
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.92), rgba(248, 250, 252, 0.7));
}

.sidebar-header h3 {
    font-size: 1.4rem;
    color: var(--text);
    letter-spacing: -0.03em;
}

.btn-icon {
    width: 42px;
    height: 42px;
    border: 0;
    border-radius: 14px;
    font-size: 1.4rem;
    cursor: pointer;
}

.create-chat-form,
.add-user-container {
    display: flex;
    gap: 10px;
    padding: 16px;
    background: rgba(255, 255, 255, 0.55);
    border-bottom: 1px solid var(--line);
}

.create-chat-form button,
.add-user-container button {
    flex-shrink: 0;
    border: 0;
    border-radius: 14px;
    padding: 12px 16px;
    cursor: pointer;
    font-weight: 700;
}

.chats-list {
    flex: 1;
    padding: 10px;
    overflow-y: auto;
}

.chat-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 14px;
    margin-bottom: 8px;
    padding: 16px 16px 16px 18px;
    border: 1px solid transparent;
    border-radius: 20px;
    cursor: pointer;
    transition:
        background-color 0.24s ease,
        border-color 0.24s ease,
        transform 0.24s ease,
        box-shadow 0.24s ease;
}

.chat-item:hover {
    background: rgba(255, 255, 255, 0.82);
    border-color: rgba(15, 23, 42, 0.06);
    box-shadow: var(--shadow-sm);
}

.chat-item.active {
    background:
        linear-gradient(135deg, rgba(115, 212, 255, 0.2), rgba(42, 157, 244, 0.14));
    border-color: rgba(42, 157, 244, 0.18);
    box-shadow: 0 16px 30px rgba(25, 118, 210, 0.14);
}

.chat-info {
    min-width: 0;
    flex: 1;
}

.chat-info strong {
    display: block;
    margin-bottom: 4px;
    color: var(--text);
    font-size: 1rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.chat-info small {
    color: var(--text-soft);
    font-size: 0.82rem;
}

.btn-edit {
    border: 0;
    border-radius: 12px;
    padding: 8px 10px;
    background: rgba(15, 23, 42, 0.05);
    color: var(--text-muted);
    cursor: pointer;
}

.btn-edit:hover {
    background: rgba(15, 23, 42, 0.1);
    color: var(--text);
}

.sidebar-footer {
    padding: 18px;
    border-top: 1px solid var(--line);
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.6), rgba(248, 250, 252, 0.92));
}

.user-info {
    margin-bottom: 12px;
    padding: 14px 16px;
    border-radius: 18px;
    background: rgba(255, 255, 255, 0.86);
    border: 1px solid rgba(148, 163, 184, 0.18);
    color: var(--text);
    text-align: center;
    font-weight: 700;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.6);
}

.btn-logout {
    width: 100%;
    padding: 13px 16px;
    border: 0;
    border-radius: 16px;
    background: linear-gradient(135deg, #ef4444 0%, #b91c1c 100%);
    color: #ffffff;
    font-weight: 800;
    cursor: pointer;
    box-shadow: 0 14px 28px rgba(185, 28, 28, 0.2);
}

.btn-logout:hover {
    box-shadow: 0 16px 30px rgba(185, 28, 28, 0.26);
}

/* Chat Area */
.chat-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    border-radius: 34px;
    overflow: hidden;
    background:
        radial-gradient(circle at top right, rgba(115, 212, 255, 0.12), transparent 24%),
        linear-gradient(180deg, rgba(255, 255, 255, 0.78), rgba(241, 245, 249, 0.92));
}

.chat-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
    padding: 24px 28px 22px;
    border-bottom: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.7);
}

.chat-title h2 {
    color: var(--text);
    font-size: clamp(1.5rem, 2vw, 1.9rem);
    letter-spacing: -0.035em;
}

.member-count {
    display: inline-block;
    margin-top: 4px;
    color: var(--text-soft);
    font-size: 0.86rem;
}

.chat-header > div:last-child {
    display: flex;
    align-items: center;
    gap: 10px;
}

.btn-add-user {
    border: 0;
    border-radius: 15px;
    padding: 12px 18px;
    cursor: pointer;
    font-weight: 800;
}

.members-btn {
    background: linear-gradient(135deg, #1d3f6e 0%, #2a72cf 100%);
    box-shadow: 0 16px 30px rgba(29, 63, 110, 0.22);
}

.members-btn:hover {
    box-shadow: 0 18px 34px rgba(29, 63, 110, 0.28);
}

.messages-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 14px;
    padding: 24px 28px;
    overflow-y: auto;
    background:
        radial-gradient(circle at 10% 20%, rgba(78, 197, 255, 0.08), transparent 20%),
        radial-gradient(circle at 92% 8%, rgba(42, 157, 244, 0.1), transparent 18%);
}

.message {
    max-width: min(680px, 72%);
    padding: 14px 16px 13px;
    border-radius: 22px;
    animation: fadeIn 0.3s ease;
    box-shadow: var(--shadow-sm);
}

.message.own {
    align-self: flex-end;
    border-bottom-right-radius: 8px;
    background: linear-gradient(135deg, #1976d2 0%, #2a9df4 58%, #67c8ff 100%);
    color: #ffffff;
}

.message.other {
    align-self: flex-start;
    border-bottom-left-radius: 8px;
    background: rgba(255, 255, 255, 0.92);
    color: var(--text);
    border: 1px solid rgba(148, 163, 184, 0.14);
}

.message-header {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 7px;
    font-size: 0.76rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

.message.own .message-header {
    color: rgba(255, 255, 255, 0.78);
}

.message.other .message-header {
    color: var(--text-soft);
}

.message-content {
    word-break: break-word;
    line-height: 1.55;
}

.message-input-area {
    display: flex;
    align-items: flex-end;
    gap: 14px;
    padding: 20px 24px 24px;
    border-top: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.72);
}

.message-input-area textarea {
    min-height: 56px;
    max-height: 180px;
    resize: vertical;
    background: rgba(255, 255, 255, 0.95);
}

.btn-send {
    min-width: 120px;
    padding: 16px 24px;
    border: 0;
    border-radius: 18px;
    cursor: pointer;
    font-weight: 800;
}

.no-chat-selected {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 16px;
    height: 100%;
    padding: 40px 24px;
    color: var(--text-muted);
    text-align: center;
}

.no-chat-selected p {
    max-width: 360px;
    font-size: 1.02rem;
}

.no-chat-selected button {
    border: 0;
    border-radius: 18px;
    padding: 14px 22px;
    cursor: pointer;
    font-weight: 800;
}

.loading {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    color: #f8fafc;
    font-size: clamp(1.4rem, 3vw, 2rem);
    font-weight: 800;
    letter-spacing: -0.03em;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 1000;
    justify-content: center;
    align-items: center;
    padding: 20px;
    background: rgba(2, 6, 23, 0.5);
    backdrop-filter: blur(10px);
}

.modal-content {
    width: 100%;
    max-width: 420px;
    border-radius: 28px;
    padding: 28px;
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(248, 250, 252, 0.94));
    box-shadow: var(--shadow-lg);
    animation: slideUp 0.28s ease;
}

.modal-content h3 {
    margin-bottom: 18px;
    color: var(--text);
    font-size: 1.35rem;
    letter-spacing: -0.03em;
}

.modal-content ul {
    list-style: none;
    max-height: 320px;
    overflow-y: auto;
    border-radius: 18px;
    border: 1px solid var(--line);
    background: rgba(255, 255, 255, 0.72);
}

.modal-content li {
    padding: 12px 14px;
    color: var(--text-muted);
    border-bottom: 1px solid rgba(15, 23, 42, 0.06);
}

.modal-content li:last-child {
    border-bottom: 0;
}

.modal-content button {
    width: 100%;
    margin-top: 18px;
    border: 0;
    border-radius: 16px;
    padding: 13px 16px;
    cursor: pointer;
    font-weight: 800;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

::-webkit-scrollbar-track {
    background: rgba(148, 163, 184, 0.12);
    border-radius: 999px;
}

::-webkit-scrollbar-thumb {
    background: linear-gradient(180deg, rgba(115, 212, 255, 0.9), rgba(42, 157, 244, 0.9));
    border: 2px solid transparent;
    border-radius: 999px;
    background-clip: padding-box;
}

::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(180deg, rgba(78, 197, 255, 0.95), rgba(25, 118, 210, 0.95));
    border: 2px solid transparent;
    background-clip: padding-box;
}

@media (max-width: 1080px) {
    .chat-room {
        padding: 12px;
        gap: 12px;
    }

    .sidebar {
        width: 290px;
    }

    .message {
        max-width: 82%;
    }
}

@media (max-width: 860px) {
    .chat-room {
        flex-direction: column;
        min-height: auto;
    }

    .sidebar {
        width: 100%;
        max-height: 42vh;
    }

    .chat-area {
        min-height: 56vh;
    }

    .chat-header {
        flex-direction: column;
        align-items: stretch;
    }

    .chat-header > div:last-child {
        justify-content: stretch;
        flex-wrap: wrap;
    }

    .chat-header > div:last-child button {
        flex: 1 1 180px;
    }

    .message {
        max-width: 90%;
    }
}

@media (max-width: 640px) {
    body::before {
        background-size: 24px 24px;
    }

    .auth-container {
        padding: 16px;
    }

    .auth-card {
        padding: 32px 22px 26px;
        border-radius: 24px;
    }

    .chat-room {
        padding: 8px;
    }

    .sidebar,
    .chat-area {
        border-radius: 24px;
    }

    .sidebar-header,
    .chat-header,
    .messages-container,
    .message-input-area {
        padding-left: 16px;
        padding-right: 16px;
    }

    .create-chat-form,
    .add-user-container,
    .message-input-area {
        flex-direction: column;
    }

    .create-chat-form button,
    .add-user-container button,
    .btn-send {
        width: 100%;
    }

    .message {
        max-width: 100%;
    }
}