/* B) CSS Code */
.webp-converter {
    --primary: #F97316;
    --primary-dark: #C2410C;
    --black: #1A1A1A;
    --gray-border: #E5E5E5;
    --bg-light: #FFFFFF;
    font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    max-width: 900px;
    margin: 0 auto;
    background: var(--bg-light);
    border-radius: 28px;
    box-shadow: 0 25px 50px -12px rgba(0,0,0,0.15);
    padding: 2rem 1.8rem;
    transition: all 0.2s ease;
    border: 1px solid #f0f0f0;
}

.tool-heading {
    font-size: 2.2rem;
    font-weight: 700;
    color: var(--black);
    margin: 0 0 0.25rem 0;
    letter-spacing: -0.02em;
    line-height: 1.2;
}
.tool-heading::after {
    content: '';
    display: block;
    width: 70px;
    height: 4px;
    background: var(--primary);
    border-radius: 4px;
    margin-top: 8px;
}

.tool-description {
    font-size: 1rem;
    color: #4B5563;
    margin-bottom: 1.75rem;
}

/* upload area */
.upload-section {
    border: 2px dashed var(--gray-border);
    border-radius: 24px;
    background: #FAFAFA;
    padding: 2.8rem 1.5rem;
    text-align: center;
    cursor: pointer;
    transition: border 0.2s, background 0.2s;
    margin-bottom: 1.5rem;
    position: relative;
}
.upload-section:hover {
    border-color: var(--primary);
    background: #FFF8F0;
}
.upload-icon svg {
    stroke: var(--primary);
    margin-bottom: 0.5rem;
}
.upload-text {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--black);
    margin: 0.5rem 0 0.25rem;
}
.orange-text {
    color: var(--primary);
    font-weight: 600;
}
.upload-hint {
    font-size: 0.85rem;
    color: #6B7280;
}
.file-input {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}

/* conversion panel */
.conversion-panel {
    background: #FFFFFF;
    border-radius: 24px;
    padding: 1.2rem;
    margin: 1rem 0 1.8rem;
    border: 1px solid #EEEEEE;
    box-shadow: 0 8px 20px rgba(0,0,0,0.02);
}
.conversion-panel.hidden {
    display: none;
}

.dual-preview {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin-bottom: 1.5rem;
}
.preview-box {
    background: #F9FAFB;
    border-radius: 16px;
    padding: 1rem;
    border: 1px solid #F0F0F0;
}
.box-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--black);
    margin: 0 0 0.75rem 0;
    text-align: center;
}
.image-wrapper {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 160px;
    margin-bottom: 0.75rem;
}
.image-wrapper img {
    max-width: 100%;
    max-height: 160px;
    object-fit: contain;
    border-radius: 8px;
}
.webp-bg {
    background: repeating-conic-gradient(#E5E5E5 0% 25%, #FFFFFF 0% 50%) 50% / 20px 20px;
    border-radius: 8px;
}
.image-info {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
    font-size: 0.8rem;
    background: #FFFFFF;
    padding: 0.5rem;
    border-radius: 30px;
    border: 1px solid #EEEEEE;
}
.info-label {
    color: #6B7280;
    margin-left: 0.25rem;
}
.info-label:first-child {
    margin-left: 0;
}

/* quality control */
.quality-control {
    margin: 1.5rem 0;
    padding: 0 0.5rem;
}
.quality-label {
    display: flex;
    justify-content: space-between;
    font-weight: 600;
    color: var(--black);
    margin-bottom: 0.5rem;
}
.quality-badge {
    background: #FFF2E5;
    color: var(--primary);
    padding: 0.2rem 0.8rem;
    border-radius: 30px;
    font-size: 0.85rem;
}
#webpQuality {
    width: 100%;
    height: 6px;
    background: #E0E0E0;
    border-radius: 10px;
    -webkit-appearance: none;
    margin-bottom: 0.25rem;
}
#webpQuality::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 22px;
    height: 22px;
    background: var(--primary);
    border-radius: 50%;
    cursor: pointer;
    border: 2px solid white;
    box-shadow: 0 2px 8px rgba(249,115,22,0.4);
}
#webpQuality::-webkit-slider-thumb:hover {
    background: var(--primary-dark);
}
.quality-hint {
    font-size: 0.7rem;
    color: #9CA3AF;
    text-align: right;
}

/* action buttons */
.action-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    justify-content: center;
    margin-top: 1rem;
}
.btn {
    background: white;
    border: 1.5px solid var(--primary);
    color: var(--primary);
    font-weight: 600;
    padding: 0.8rem 2rem;
    border-radius: 50px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.2s;
    letter-spacing: 0.3px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.02);
    min-width: 200px;
}
.btn:hover {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
    box-shadow: 0 8px 18px rgba(249,115,22,0.25);
    transform: translateY(-1px);
}
.convert-btn {
    background: var(--primary);
    color: white;
}
.convert-btn:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
}
.download-btn {
    background: var(--black);
    border-color: var(--black);
    color: white;
}
.download-btn:hover {
    background: #000;
    border-color: #000;
}
.hidden {
    display: none;
}
.disclaimer {
    font-size: 0.75rem;
    color: #9CA3AF;
    margin-top: 0.75rem;
    text-align: center;
}

/* feature grid */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
    margin-top: 2rem;
    border-top: 1px solid var(--gray-border);
    padding-top: 1.5rem;
}
.feature-item {
    text-align: center;
    background: #FEFCF9;
    padding: 0.9rem 0.2rem;
    border-radius: 32px;
    transition: all 0.2s;
    border: 1px solid transparent;
}
.feature-item:hover {
    border-color: var(--primary);
    background: white;
    transform: scale(1.02);
}
.feature-icon {
    font-size: 1.7rem;
    display: block;
    line-height: 1.2;
    color: var(--primary);
}
.feature-text {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--black);
    text-transform: uppercase;
    letter-spacing: 0.3px;
}

/* responsive */
@media (max-width: 650px) {
    .dual-preview {
        grid-template-columns: 1fr;
    }
    .webp-converter { padding: 1.5rem 1rem; }
    .tool-heading { font-size: 1.9rem; }
    .feature-grid { grid-template-columns: repeat(2, 1fr); gap: 0.7rem; }
    .action-buttons { flex-direction: column; }
    .btn { width: 100%; }
}
@media (max-width: 380px) {
    .feature-grid { grid-template-columns: 1fr; }
    .image-info { flex-direction: column; align-items: center; }
}