:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --primary-light: #eef2ff;
    --secondary-color: #10b981;
    --secondary-hover: #059669;
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    --red-100: #fee2e2;
    --red-500: #ef4444;
    --yellow-100: #fef3c7;
    --yellow-500: #f59e0b;
    --green-100: #d1fae5;
    --green-500: #10b981;
    --blue-100: #dbeafe;
    --blue-500: #3b82f6;
    --purple-100: #ede9fe;
    --purple-500: #8b5cf6;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--gray-50);
    color: var(--gray-800);
    line-height: 1.5;
}

/* Layout */
.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

.research-portal {
    display: grid;
    gap: 2rem;
    grid-template-columns: 1fr;
}

    .research-portal.desktop {
        grid-template-columns: 300px 1fr;
    }

/* Header */
.portal-header {
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--gray-200);
}

.portal-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 0.5rem;
}

.portal-subtitle {
    color: var(--gray-600);
    font-size: 1.1rem;
}

/* Sidebar */
.sidebar {
    background-color: white;
    border-radius: 1rem;
    border: 1px solid var(--gray-200);
    box-shadow: var(--shadow);
    max-width: 300px;
    height: auto;
    max-height: calc(100vh - 4rem);
    overflow-y: auto;
    transition: all 0.3s ease;
}

    .sidebar.desktop {
        position: sticky;
        top: 2rem;
    }

.sidebar-header {
    padding: 1.5rem 1.5rem 0.5rem;
    border-bottom: 1px solid var(--gray-200);
}

.sidebar-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--gray-900);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.sidebar-content {
    padding: 1.5rem;
}

/* Form Elements */
.form-group {
    margin-bottom: 1.5rem;
}

.form-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--gray-700);
    margin-bottom: 0.5rem;
}

.form-input,
.form-select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--gray-300);
    border-radius: 0.5rem;
    background-color: white;
    color: var(--gray-900);
    font-size: 0.95rem;
    transition: all 0.2s ease;
}

    .form-input:focus,
    .form-select:focus {
        outline: none;
        border-color: var(--primary-color);
        box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.15);
    }

    .form-input::placeholder {
        color: var(--gray-400);
    }

.search-input-wrapper {
    position: relative;
}

.search-icon {
    position: absolute;
    left: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--gray-500);
}

.search-input {
    padding-left: 2.5rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.25rem;
    font-weight: 500;
    font-size: 0.95rem;
    border-radius: 0.5rem;
    transition: all 0.2s ease;
    cursor: pointer;
    border: none;
}

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

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

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

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

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--gray-300);
    color: var(--gray-700);
}

    .btn-outline:hover {
        border-color: var(--gray-400);
        background-color: var(--gray-100);
    }

.btn-sm {
    padding: 0.5rem 0.75rem;
    font-size: 0.875rem;
}

.btn-icon {
    padding: 0.5rem;
    border-radius: 0.375rem;
}

.w-100 {
    width: 100%;
}

/* Paper Cards */
.paper-card {
    background-color: white;
    border-radius: 1rem;
    border: 1px solid var(--gray-200);
    box-shadow: var(--shadow);
    transition: all 0.2s ease;
    overflow: hidden;
}

    .paper-card:hover {
        box-shadow: var(--shadow-md);
        transform: translateY(-2px);
    }

.paper-content {
    padding: 1.75rem;
}

.paper-title {
    font-size: 1.35rem;
    font-weight: 600;
    color: var(--gray-900);
    margin-bottom: 0.75rem;
    line-height: 1.3;
}

    .paper-title a {
        color: inherit;
        text-decoration: none;
    }

        .paper-title a:hover {
            color: var(--primary-color);
        }

.paper-abstract {
    color: var(--gray-600);
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.paper-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
    margin-top: 1.5rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--gray-200);
}

.paper-stats {
    display: flex;
    gap: 1.25rem;
    margin-top: 1rem;
}

.paper-stat {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--gray-600);
    font-size: 0.875rem;
}

.paper-authors {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.author-chip {
    display: inline-flex;
    align-items: center;
    padding: 0.25rem 0.75rem;
    background-color: var(--gray-100);
    border-radius: 9999px;
    font-size: 0.875rem;
    color: var(--gray-700);
}

/* Badges */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 0.35rem 0.85rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: 9999px;
}

.badge-field {
    background-color: var(--purple-100);
    color: var(--purple-500);
}

.badge-engineering {
    background-color: var(--blue-100);
    color: var(--blue-500);
}

.badge-construction {
    background-color: var(--yellow-100);
    color: var(--yellow-500);
}

.badge-technology {
    background-color: var(--green-100);
    color: var(--green-500);
}

.badge-open {
    background-color: var(--green-100);
    color: var(--green-500);
}

.badge-restricted {
    background-color: var(--yellow-100);
    color: var(--yellow-500);
}

/* Sort and Filter Controls */
.controls-wrapper {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.sort-wrapper {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.sort-label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--gray-700);
}

.view-toggle {
    display: flex;
    gap: 0.5rem;
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem 2rem;
    background-color: white;
    border-radius: 1rem;
    box-shadow: var(--shadow);
}

.empty-state-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 1.5rem;
    color: var(--gray-400);
}

.empty-state-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--gray-800);
    margin-bottom: 0.75rem;
}

.empty-state-text {
    color: var(--gray-600);
    max-width: 400px;
    margin: 0 auto 1.5rem;
}

/* Utility Classes */
.text-sm {
    font-size: 0.875rem;
}

.text-gray {
    color: var(--gray-600);
}

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

.mb-1 {
    margin-bottom: 0.25rem;
}

.mb-2 {
    margin-bottom: 0.5rem;
}

.mb-4 {
    margin-bottom: 1rem;
}

.mb-6 {
    margin-bottom: 1.5rem;
}

.ml-2 {
    margin-left: 0.5rem;
}

.mr-2 {
    margin-right: 0.5rem;
}

.space-y-4 > * + * {
    margin-top: 1rem;
}

.space-y-6 > * + * {
    margin-top: 1.5rem;
}

.flex {
    display: flex;
}

.flex-col {
    flex-direction: column;
}

.justify-between {
    justify-content: space-between;
}

.items-center {
    align-items: center;
}

.items-start {
    align-items: flex-start;
}

.gap-2 {
    gap: 0.5rem;
}

.gap-4 {
    gap: 1rem;
}

/* Responsive Adjustments */
@media (max-width: 768px) {
    .controls-wrapper {
        flex-direction: column;
        align-items: flex-start;
    }

    .sort-wrapper {
        width: 100%;
    }

        .sort-wrapper .form-select {
            flex-grow: 1;
        }

    .paper-meta {
        flex-direction: column;
        align-items: flex-start;
    }
}
/* Additional styles for mobile filter toggle */
@media (max-width: 1023px) {
    #filterToggleBtn {
        display: flex;
    }

    .sidebar {
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        max-width: 100%;
        max-height: 100%;
        z-index: 100;
        border-radius: 0;
        transform: translateX(-100%);
        transition: transform 0.3s ease;
    }

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

    .sidebar-header {
        display: flex;
        justify-content: space-between;
        align-items: center;
        padding: 1.5rem;
    }

        .sidebar-header::after {
            content: "×";
            font-size: 1.75rem;
            cursor: pointer;
        }
}

/* Add this to your research-portal.css file */
.truncated-abstract {
    display: -webkit-box;
    -webkit-line-clamp: 4;
    -webkit-box-orient: vertical;
    overflow: hidden;
    text-overflow: ellipsis;
    max-height: 6em; /* Fallback for browsers that don't support line-clamp */
}