:root {
    /* Color Palette - Lark Style */
    --primary-color: #3370ff;
    --primary-hover: #285dc9;
    --bg-color: #f5f6f7;
    --card-bg: #ffffff;
    --text-primary: #1f2329;
    --text-secondary: #646a73;
    --text-tertiary: #8f959e;
    --border-color: #dee0e3;
    --divider-color: #ebedf0;
    --success-bg: #e6fffa;
    --success-text: #007a5e;
    --error-bg: #fff5f5;
    --error-text: #c53030;
    --focus-ring: rgba(51, 112, 255, 0.2);
    
    /* Spacing & Radius */
    --radius-md: 8px;
    --radius-sm: 4px;
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.08);
    
    /* Transition */
    --transition-fast: 0.2s ease;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

.app-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
    height: 100vh;
    grid-template-rows: auto 1fr;
}

@media (min-width: 768px) {
    .app-container {
        grid-template-columns: 350px 1fr;
        padding: 40px var(--spacing-lg);
    }
}

/* Responsive Design */
@media (max-width: 768px) {
    .app-container {
        flex-direction: column;
        padding: 10px;
    }

    .left-col, .right-col {
        width: 100%;
        max-width: 100%;
    }

    .card {
        padding: 15px;
    }

    .header {
        padding: 10px 15px;
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .card-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .filters {
        width: 100%;
        flex-wrap: wrap;
    }
    
    .filters input {
        flex: 1;
        min-width: 100px;
    }
    
    .message-list {
        max-height: 500px; /* Limit height on mobile so page can scroll */
    }
}

/* Header */
.header {
    grid-column: 1 / -1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--spacing-sm);
}

.logo {
    font-size: 24px;
    font-weight: 600;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.logo svg {
    width: 32px;
    height: 32px;
    color: var(--primary-color);
}

/* Cards */
.card {
    background: var(--card-bg);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    padding: var(--spacing-lg);
    border: 1px solid var(--border-color);
    height: fit-content;
}

.card-header {
    margin-bottom: var(--spacing-lg);
    border-bottom: 1px solid var(--divider-color);
    padding-bottom: var(--spacing-sm);
}

.card-title {
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
}

/* Forms */
.form-group {
    margin-bottom: var(--spacing-md);
}

.form-label {
    display: block;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.form-input {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 14px;
    color: var(--text-primary);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    background: #fff;
}

.form-input.small {
    padding: 6px 10px;
    font-size: 13px;
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--focus-ring);
}

.form-input::placeholder {
    color: var(--text-tertiary);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    font-size: 14px;
    font-weight: 500;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    border: none;
    gap: 8px;
}

.btn.small {
    padding: 6px 12px;
    font-size: 13px;
}

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

.btn-primary:hover {
    background-color: var(--primary-hover);
    box-shadow: 0 2px 8px rgba(51, 112, 255, 0.3);
}

.btn-secondary {
    background-color: #f0f2f5; /* Light gray */
    color: var(--text-primary);
}

.btn-secondary:hover {
    background-color: #e4e6eb;
}

.btn-block {
    width: 100%;
}

.btn:active {
    transform: translateY(1px);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

/* Message List */
.message-list-container {
    display: flex;
    flex-direction: column;
    flex-grow: 1;
    overflow: hidden; /* Contains scroll */
    min-height: 400px;
}

.message-list {
    flex-grow: 1;
    overflow-y: auto;
    padding-right: 4px;
    display: flex;
    flex-direction: column;
}

/* Custom Scrollbar */
.message-list::-webkit-scrollbar {
    width: 6px;
}
.message-list::-webkit-scrollbar-track {
    background: transparent;
}
.message-list::-webkit-scrollbar-thumb {
    background-color: #dcdcdc;
    border-radius: 3px;
}
.message-list::-webkit-scrollbar-thumb:hover {
    background-color: #c0c0c0;
}

.message-item {
    display: flex;
    flex-direction: column;
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--divider-color);
    transition: background-color var(--transition-fast);
    animation: fadeIn 0.3s ease-out;
}

.message-item:hover {
    background-color: #fcfcfd;
}

.message-item:last-child {
    border-bottom: none;
}

.date-divider {
    padding: 8px 16px;
    background-color: #f5f6f7;
    color: var(--text-secondary);
    font-size: 12px;
    font-weight: 600;
    position: sticky;
    top: 0;
    z-index: 10;
    border-bottom: 1px solid var(--border-color);
}

.message-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-xs);
}

.message-time {
    font-size: 12px;
    color: var(--text-tertiary);
    font-variant-numeric: tabular-nums;
}

.message-status {
    font-size: 12px;
    padding: 2px 8px;
    border-radius: 12px;
    font-weight: 500;
}

.status-sent {
    background-color: var(--success-bg);
    color: var(--success-text);
}

.status-failed {
    background-color: var(--error-bg);
    color: var(--error-text);
}

.message-content {
    font-size: 14px;
    color: var(--text-primary);
    white-space: pre-wrap;
    word-break: break-word;
    line-height: 1.6;
}

/* Structured Message Card */
.message-card {
    background-color: #f8f9fa;
    border-radius: var(--radius-sm);
    padding: 10px;
    border: 1px solid var(--border-color);
}

.message-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
    padding-bottom: 8px;
    border-bottom: 1px dashed var(--divider-color);
}

.device-name {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 13px;
}

.app-name {
    font-size: 12px;
    color: var(--text-secondary);
    background-color: rgba(51, 112, 255, 0.1);
    color: var(--primary-color);
    padding: 2px 6px;
    border-radius: 4px;
}

.message-body {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.msg-row {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    font-size: 13px;
}

.msg-label {
    color: var(--text-tertiary);
    min-width: 40px;
    flex-shrink: 0;
}

.msg-val {
    color: var(--text-secondary);
}

.msg-val.highlight {
    color: var(--text-primary);
    font-weight: 500;
}

.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-tertiary);
    margin: auto;
}

.empty-state svg {
    width: 48px;
    height: 48px;
    margin-bottom: var(--spacing-md);
    opacity: 0.5;
}

.loading-state {
    text-align: center;
    padding: 40px;
    color: var(--text-secondary);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    margin: auto;
}

.spinner-dark {
    width: 24px;
    height: 24px;
    border: 2px solid rgba(0,0,0,0.1);
    border-radius: 50%;
    border-top-color: var(--primary-color);
    animation: spin 0.8s linear infinite;
}

/* Pagination & Filters */
.filters {
    display: flex;
    gap: 8px;
    align-items: center;
}

.pagination-controls {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 10px;
    border-top: 1px solid var(--divider-color);
    gap: 15px;
    font-size: 13px;
    color: var(--text-secondary);
}

/* Toast */
.toast-container {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 1000;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.toast {
    background-color: rgba(31, 35, 41, 0.9);
    color: white;
    padding: 12px 24px;
    border-radius: var(--radius-md);
    font-size: 14px;
    box-shadow: var(--shadow-md);
    opacity: 0;
    transform: translateY(20px);
    transition: all 0.3s cubic-bezier(0.18, 0.89, 0.32, 1.28);
    display: flex;
    align-items: center;
    gap: 8px;
}

.toast.show {
    opacity: 1;
    transform: translateY(0);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(5px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Loader */
.spinner {
    width: 16px;
    height: 16px;
    border: 2px solid rgba(255,255,255,0.3);
    border-radius: 50%;
    border-top-color: #fff;
    animation: spin 0.8s linear infinite;
    display: none;
}

.btn.loading .spinner {
    display: inline-block;
}
.btn.loading span {
    display: none;
}

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