:root {
    --primary-color: #4f46e5;
    --primary-light: #6366f1;
    --secondary-color: #475569;
    --success-color: #059669;
    --background-color: #0f172a;
    --card-background: rgba(255, 255, 255, 0.02);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border-color: rgba(255, 255, 255, 0.08);
    --glass-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.37);
    --glass-border: 1px solid rgba(255, 255, 255, 0.18);
    --label-gradient: linear-gradient(90deg, #34d399, #2dd4bf);
    --label-accent: #14b8a6;
}

body {
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    color: var(--text-primary);
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    position: relative;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle at center, rgba(99, 102, 241, 0.15) 0%, transparent 50%, #0f172a 100%);
    opacity: 0.9;
    z-index: -1;
    animation: gradientMove 15s ease-in-out infinite;
}

@keyframes gradientMove {
    0% { transform: translate(0, 0) rotate(0deg); }
    25% { transform: translate(-40px, 20px) rotate(3deg); }
    50% { transform: translate(0, 40px) rotate(0deg); }
    75% { transform: translate(40px, -20px) rotate(-3deg); }
    100% { transform: translate(0, 0) rotate(0deg); }
}

.card {
    background: var(--card-background);
    border: var(--glass-border);
    box-shadow: var(--glass-shadow);
    border-radius: 1.5rem;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(
        90deg,
        transparent,
        rgba(255, 255, 255, 0.05),
        transparent
    );
    transition: 0.5s;
    pointer-events: none;
}

.card:hover::before {
    left: 100%;
}

.card:hover {
    transform: translateY(-5px) scale(1.01);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
    background: rgba(31, 41, 55, 0.7);
}

.card-body {
    position: relative;
    z-index: 2;
}

.form-control {
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 1rem;
    color: var(--text-primary) !important;
    padding: 1rem 1.25rem;
    transition: all 0.3s ease;
}

.form-control:focus {
    background: rgba(255, 255, 255, 0.05);
    border-color: var(--primary-light);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
    color: var(--text-primary) !important;
}

#transform-input {
    background: rgba(255, 255, 255, 0.03);
    color: var(--text-primary) !important;
}

#transform-input:focus {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary) !important;
}

.btn {
    border-radius: 1rem;
    padding: 0.875rem 1.75rem;
    font-weight: 600;
    letter-spacing: 0.025em;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
    border: none;
}

.btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 300%;
    height: 300%;
    background: radial-gradient(circle, rgba(255,255,255,0.2) 0%, transparent 60%);
    transform: translate(-50%, -50%) scale(0);
    transition: transform 0.6s ease-out;
}

.btn:hover::before {
    transform: translate(-50%, -50%) scale(1);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    box-shadow: 0 4px 15px rgba(79, 70, 229, 0.3);
}

.btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(79, 70, 229, 0.4);
}

.btn-success {
    background: linear-gradient(135deg, var(--success-color), #10b981);
    box-shadow: 0 4px 15px rgba(5, 150, 105, 0.3);
}

.btn-success:hover {
    background: linear-gradient(135deg, #10b981, var(--success-color));
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(5, 150, 105, 0.4);
}

.sentence-result {
    background: rgba(255, 255, 255, 0.03);
    border-radius: 1rem;
    padding: 1.25rem;
    margin-bottom: 1rem;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.sentence-result:hover {
    transform: translateX(10px) scale(1.02);
    background: rgba(31, 41, 55, 0.7);
    border-color: rgba(255, 255, 255, 0.1);
}

.badge {
    font-size: 0.9em;
    padding: 0.6rem 1.2rem;
    border-radius: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.025em;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
    text-transform: uppercase;
}

.level-info-vertical .badge {
    width: 100%;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: all 0.3s ease;
}

.level-info-vertical .badge:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
}

#sentences-container::-webkit-scrollbar,
#transformed-sentences-container::-webkit-scrollbar {
    width: 6px;
}

#sentences-container::-webkit-scrollbar-track,
#transformed-sentences-container::-webkit-scrollbar-track {
    background: rgba(255, 255, 255, 0.05);
    border-radius: 3px;
}

#sentences-container::-webkit-scrollbar-thumb,
#transformed-sentences-container::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 3px;
}

.form-check-input {
    width: 1.25rem;
    height: 1.25rem;
    margin-right: 0.75rem;
    cursor: pointer;
    background-color: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: all 0.3s ease;
}

.form-check-input:checked {
    animation: checkmark 0.3s ease-in-out;
}

@keyframes checkmark {
    0% { transform: scale(1); }
    50% { transform: scale(1.2); }
    100% { transform: scale(1); }
}

.footer {
    background: linear-gradient(to top, rgba(15, 23, 42, 0.95), transparent);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-top: var(--glass-border);
}

.footer a.text-muted {
    transition: all 0.3s ease;
    position: relative;
}

.footer a.text-muted:hover {
    color: var(--label-accent) !important;
    transform: translateX(3px);
}

.footer ul li a {
    position: relative;
    transition: all 0.3s ease;
}

.footer ul li a:hover {
    color: var(--label-accent) !important;
    transform: translateX(3px);
}

.footer ul li a::before {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 1px;
    background: var(--label-gradient);
    transition: width 0.3s ease;
}

.footer ul li a:hover::before {
    width: 100%;
}

.social-links a {
    font-size: 1.5em;
    color: var(--text-secondary) !important;
    transition: all 0.3s ease;
    position: relative;
}

.social-links a::before {
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at center, var(--primary-light) 0%, transparent 70%);
    opacity: 0;
    transform: scale(0);
    transition: all 0.3s ease;
}

.social-links a:hover {
    color: var(--primary-light) !important;
    transform: translateY(-3px);
}

.social-links a:hover::before {
    opacity: 0.2;
    transform: scale(1.5);
}

h3.text-primary {
    color: var(--text-primary) !important;
    font-weight: 700;
    letter-spacing: -0.03em;
    position: relative;
    display: inline-block;
    padding-bottom: 0.5rem;
}

h3.text-primary::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-color), transparent);
}

@media (max-width: 768px) {
    .container-fluid {
        padding: 1rem;
    }
    
    .card {
        margin-bottom: 1.5rem;
    }
    
    .btn {
        width: 100%;
    }
    
    .footer {
        text-align: center;
        padding: 2rem 1rem;
    }
    
    .social-links {
        justify-content: center;
        margin-top: 1.5rem;
    }
    
    .custom-select {
        font-size: 0.95rem;
        padding: 0.875rem 2.5rem 0.875rem 1rem;
    }
    
    .select-arrow {
        right: 1rem;
        font-size: 0.75rem;
    }
    
    .model-selection-wrapper {
        margin-bottom: 0.5rem;
    }
}

.form-label {
    font-size: 1.15rem;
    font-weight: 500;
    letter-spacing: 0.01em;
    background: var(--label-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    display: inline-block;
    position: relative;
    margin-bottom: 1.2rem;
    padding-left: 1.2rem;
    opacity: 0.85;
    transition: all 0.3s ease;
    text-shadow: 0 0 20px rgba(52, 211, 153, 0.1);
}

.form-label:hover {
    opacity: 1;
    transform: translateX(3px);
    text-shadow: 0 0 25px rgba(52, 211, 153, 0.2);
}

.form-label::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 3px;
    height: 1em;
    background: var(--label-accent);
    border-radius: 4px;
    opacity: 0.6;
    box-shadow: 0 0 12px var(--label-accent);
}

.form-label::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 1.2rem;
    width: 3rem;
    height: 1px;
    background: var(--label-gradient);
    opacity: 0.4;
    transition: width 0.3s ease;
}

.form-label:hover::after {
    width: 5rem;
    opacity: 0.7;
}

.form-check-label {
    font-weight: 500;
    letter-spacing: 0.02em;
    transition: all 0.3s ease;
    opacity: 0.75;
    color: #a5f3fc;
}

.form-check-label:hover {
    opacity: 0.9;
    transform: translateX(2px);
}

.form-check-input:checked + .form-check-label {
    background: var(--label-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    font-weight: 600;
    opacity: 1;
    text-shadow: 0 0 20px rgba(52, 211, 153, 0.2);
}

/* Custom Select Dropdown Styling */
.model-selection-wrapper {
    width: 100%;
}

.custom-select-wrapper {
    position: relative;
    width: 100%;
}

.custom-select {
    width: 100%;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 1rem;
    color: var(--text-primary);
    padding: 1rem 3rem 1rem 1.25rem;
    font-size: 1rem;
    font-weight: 500;
    appearance: none;
    -webkit-appearance: none;
    -moz-appearance: none;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.custom-select:hover {
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(255, 255, 255, 0.25);
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

.custom-select:focus {
    outline: none;
    background: rgba(255, 255, 255, 0.08);
    border-color: var(--primary-light);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.15), 0 4px 20px rgba(0, 0, 0, 0.3);
}

.custom-select option {
    background: rgba(17, 24, 39, 0.98);
    color: var(--text-primary);
    padding: 0.75rem;
    border: none;
}

.custom-select option:hover {
    background: rgba(99, 102, 241, 0.2);
}

.select-arrow {
    position: absolute;
    right: 1.25rem;
    top: 50%;
    transform: translateY(-50%);
    pointer-events: none;
    color: var(--text-secondary);
    font-size: 0.875rem;
    transition: all 0.3s ease;
    z-index: 1;
}

.custom-select-wrapper:hover .select-arrow {
    color: var(--primary-light);
    transform: translateY(-50%) translateY(-2px);
}

.custom-select:focus + .select-arrow {
    color: var(--primary-light);
    transform: translateY(-50%) rotate(180deg);
}

.btn-lg {
    padding: 1rem 2rem;
    font-size: 1.1rem;
    font-weight: 600;
}

.help-button-container {
    position: fixed;
    top: 1rem;
    right: 2rem;
    z-index: 1000;
}

.help-button {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-light));
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 1rem;
    font-weight: 500;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(79, 70, 229, 0.3);
}

.help-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(79, 70, 229, 0.4);
}

.help-button i {
    font-size: 1.1em;
}

.modal-content {
    background: rgba(17, 24, 39, 0.95);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: var(--glass-border);
    border-radius: 1.5rem;
    color: var(--text-primary);
}

.modal-header {
    padding: 1.5rem 2rem;
}

.modal-body {
    padding: 2rem;
}

.modal-footer {
    padding: 1.5rem 2rem;
}

.modal-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.help-section {
    margin-bottom: 2rem;
}

.help-section:last-child {
    margin-bottom: 0;
}

.help-section h6 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--label-accent);
    display: flex;
    align-items: center;
}

.help-icon {
    background: var(--label-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
    font-size: 1rem;
    margin-right: 0.75rem;
    width: 1.5rem;
    height: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    border: 2px solid;
    border-image: var(--label-gradient) 1;
}

.help-section p {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 0;
    padding-left: 2.25rem;
}

.btn-close {
    filter: invert(1) grayscale(100%) brightness(200%);
    opacity: 0.7;
    transition: opacity 0.3s ease;
}

.btn-close:hover {
    opacity: 1;
}

@media (max-width: 768px) {
    .help-button-container {
        top: 1rem;
        right: 1rem;
    }
    
    .help-button {
        padding: 0.5rem 1rem;
        font-size: 0.9rem;
    }
    
    .modal-body {
        padding: 1.5rem;
    }
    
    .help-section h6 {
        font-size: 1rem;
    }
    
    .help-section p {
        font-size: 0.9rem;
        padding-left: 1.75rem;
    }
}

.badge-sm {
    font-size: 0.8em;
    padding: 0.4rem 0.8rem;
    border-radius: 0.5rem;
    font-weight: 600;
    letter-spacing: 0.025em;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
    text-transform: uppercase;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: all 0.3s ease;
    color: var(--text-primary);
}

.badge-sm:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.tippy-box {
    background: rgba(17, 24, 39, 0.95) !important;
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: var(--glass-border);
    border-radius: 1rem !important;
    color: var(--text-primary) !important;
    font-family: 'Inter', sans-serif;
    font-size: 0.95em;
    line-height: 1.6;
    padding: 0.5rem !important;
}

.tippy-box[data-placement^='bottom'] > .tippy-arrow::before {
    border-bottom-color: rgba(17, 24, 39, 0.95) !important;
}

.tippy-box[data-placement^='top'] > .tippy-arrow::before {
    border-top-color: rgba(17, 24, 39, 0.95) !important;
}

.original-sentence {
    padding: 0.75rem 1rem;
    border-left: 3px solid var(--label-accent);
    background: rgba(255, 255, 255, 0.03);
    border-radius: 0.5rem;
    margin: 0;
}

.changed-sentence {
    cursor: help;
    border-radius: 0.3rem;
    transition: all 0.3s ease;
    position: relative;
}

.changed-sentence:hover {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.original-sentence-display {
    padding: 1rem;
    background: rgba(255, 255, 255, 0.03);
    border-radius: 0.75rem;
    border: 1px solid rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    font-size: 0.95em;
    line-height: 1.6;
    transition: all 0.3s ease;
    margin-bottom: 1rem;
}

.changed {
    padding: 0.2rem 0.4rem;
    margin: 0 0.1rem;
    border-radius: 0.3rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.changed:hover {
    filter: brightness(1.2);
    transform: translateY(-1px);
}

#original-sentence-container {
    transition: all 0.3s ease;
}

#original-sentence-content {
    max-height: calc(100vh - 300px);
    overflow-y: auto;
}

.text-level-badge {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    font-size: 0.75rem;
    padding: 0.25rem 0.5rem;
    border-radius: 0.25rem;
    background: rgba(0, 0, 0, 0.2);
    color: var(--text-primary);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
}

.help-tooltip {
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: help;
    transition: all 0.3s ease;
}

.help-tooltip:hover {
    color: var(--label-accent);
}

.transformed-sentence-display {
    padding: 1rem;
    background: rgba(255, 255, 255, 0.02);
    border-radius: 0.75rem;
    border: 1px solid rgba(255, 255, 255, 0.08);
    color: var(--text-primary);
    font-size: 0.95em;
    line-height: 1.6;
    transition: all 0.3s ease;
}

.sentence-label {
    display: block;
    font-size: 0.8em;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    letter-spacing: 0.02em;
}

.text-content {
    position: relative;
    padding: 1rem;
    background: rgba(255, 255, 255, 0.02);
    border-radius: 0.75rem;
    min-height: 200px;
}

.btn.loading {
    position: relative;
    color: transparent !important;
    pointer-events: none;
}

.btn.loading::after {
    content: '';
    position: absolute;
    left: 50%;
    top: 50%;
    width: 20px;
    height: 20px;
    margin: -10px 0 0 -10px;
    border: 2px solid rgba(255, 255, 255, 0.2);
    border-top-color: white;
    border-radius: 50%;
    animation: button-loading-spinner 0.6s linear infinite;
}

@keyframes button-loading-spinner {
    from {
        transform: rotate(0turn);
    }
    to {
        transform: rotate(1turn);
    }
}

.site-header {
    background: rgba(17, 24, 39, 0.95);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-bottom: var(--glass-border);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.header-logo {
    max-height: 45px;
    width: auto;
    transition: transform 0.3s ease;
}

.header-logo:hover {
    transform: scale(1.05);
}