* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: #f3f6fb;
    color: #1f2b46;
}

.app-shell {
    display: grid;
    grid-template-columns: 220px 1fr 260px;
    min-height: 100vh;
}

.sidebar,
.overview {
    background: #ffffff;
    border-right: 1px solid #e9edf5;
    display: flex;
    flex-direction: column;
    padding: 14px;
}

.overview {
    border-left: 1px solid #e9edf5;
    border-right: none;
}

.logo {
    font-weight: 700;
    font-size: 18px;
    color: #0e1c3b;
    margin-bottom: 12px;
}

.nav-links {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.nav-item {
    display: block;
    text-decoration: none;
    color: #4872e3;
    font-weight: 600;
    padding: 6px 8px;
    border-radius: 8px;
}

.nav-item:hover,
.nav-item.active {
    background: #e7efff;
}

.sidebar-footer {
    margin-top: auto;
    font-size: 12px;
    color: #94a3b8;
}

.chat-area {
    display: flex;
    flex-direction: column;
    background: #ffffff;
    padding: 10px 12px;
    gap: 10px;
}

.chat-header h2 {
    margin: 0;
    font-size: 20px;
}

.chat-header small {
    color: #6b7a9b;
}

.message-list {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    padding: 8px;
    gap: 10px;
    overflow-y: auto;
}

.message {
    width: 280px;
    padding: 10px 12px;
    border-radius: 10px;
    background: #f6f8ff;
    border: 1px solid #e4eaf7;
    word-wrap: break-word;
    align-self: flex-start;
}

.message-image {
    max-width: 100%;
    max-height: 200px;
    border-radius: 8px;
    margin-top: 8px;
    display: block;
}

.from-you {
    background: #E6F0FF;
}

.message-author {
    font-size: 11px;
    color: #3f5481;
    margin-bottom: 5px;
    font-weight: 600;
}

.message-text {
    line-height: 1.4;
}

.chat-input-area {
    display: flex;
    gap: 8px;
    padding-top: 6px;
}

.chat-input-area input[type="text"] {
    flex: 1;
    padding: 10px;
    border-radius: 10px;
    border: 1px solid #d8e0ef;
    color: #2e3a5a;
    background: #f2f5ff;
}

.chat-input-area .file-input {
    padding: 8px;
    border-radius: 10px;
    border: 1px solid #d8e0ef;
    color: #2e3a5a;
    background: #f2f5ff;
    cursor: pointer;
}

.chat-input-area button {
    background: #3981ff;
    color: #ffffff;
    border: none;
    padding: 0 14px;
    border-radius: 10px;
    font-weight: 700;
    cursor: pointer;
}

.overview-card {
    background: #fbfcff;
    border: 1px solid #eaf1ff;
    border-radius: 12px;
    padding: 12px;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.overview-card h3 {
    margin: 0;
    font-size: 16px;
}

.btn {
    background: #ffffff;
    border: 1px solid #d0d8ee;
    color: #2f4f9f;
    border-radius: 8px;
    padding: 8px;
    font-weight: 700;
    cursor: pointer;
}

.btn:hover {
    background: #f1f7ff;
}