.challenges-controls {
    padding: 0;
    text-align: center;
    position: relative;
    margin: 20px auto 40px;
}

.search-filter-wrapper {
    display: flex;
    gap: 1rem;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    padding: 0 20px;
}

.search-box {
    flex: 1;
    max-width: 400px;
    display: flex;
    align-items: center;
    border: 2px solid #e0e0e0;
    border-radius: 25px;
    padding: 0.5rem 1rem;
    background-color: #f9f9f9;
    transition: border-color 0.3s ease;
}

.search-box:focus-within {
    border-color: #0073e6;
    background-color: #fff;
}

.search-icon-img {
    width: 18px;
    height: 18px;
    margin-right: 0.75rem;
    opacity: 0.6;
}

.search-input {
    flex: 1;
    border: none;
    background: transparent;
    outline: none;
    font-size: 0.95rem;
    color: #282828;
}

.search-input::placeholder {
    color: #999;
}

.filter-button-wrapper {
    position: relative;
}

.filter-btn-main {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.6rem 1.25rem;
    border: 2px solid #e0e0e0;
    background-color: #fff;
    color: #666;
    border-radius: 25px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 600;
    transition: all 0.3s ease;
    white-space: nowrap;
}

.filter-btn-main:hover {
    border-color: #0073e6;
    color: #0073e6;
}

.filter-btn-main img {
    width: 16px;
    height: 16px;
}

.filter-dropdown {
    position: absolute;
    top: calc(100% + 0.5rem);
    left: 0;
    background-color: #fff;
    border: 2px solid #e0e0e0;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    z-index: 10;
    min-width: 220px;
}

.filter-dropdown.hidden {
    display: none;
}

.filter-options {
    padding: 0.75rem 0;
}

.filter-group-title {
    padding: 0.75rem 1.25rem;
    font-size: 0.85rem;
    font-weight: 700;
    color: #0073e6;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.filter-option {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1.25rem;
    cursor: pointer;
    transition: background-color 0.2s ease;
    font-size: 0.95rem;
    color: #282828;
}

.filter-option:hover {
    background-color: #f9f9f9;
}

.filter-option input[type="radio"],
.filter-option input[type="checkbox"] {
    cursor: pointer;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

@media (max-width: 600px) {
    .search-filter-wrapper {
        flex-direction: column;
        align-items: stretch;
    }
}

/* ===== ML Challenge Section ===== */

.challenges-list {
    width: 100%;
    padding: 60px 40px;
    box-sizing: border-box;
}

/* Card */
.challenge-card {
    max-width: 1100px;
    margin: 0 auto 50px;
    background: #ffffff;
    border-radius: 20px;
    padding: 35px;
}

/* Banner Image */
.challenge-image-banner {
    width: 100%;
    overflow: hidden;
    border-radius: 14px;
    position: relative;
    height: min(260px, 38vh);
    max-height: 260px;
}

.challenge-image-banner img {
    width: 100%;
    height: 100%;
    max-height: 260px;
    display: block;
    object-fit: cover;
}

.countdown-timer {
    position: absolute;
    top: 16px;
    left: 16px;
    padding: 8px 14px;
    background: #0074e0;
    color: #fff;
    border-radius: 12px;
    font-weight: 700;
    font-size: 0.95rem;
}

.countdown-timer.is-closed {
    background: #0f0f0f;
    color: #fff;
}

/* Title */
.challenge-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-top: 24px;
}

.challenge-card h2 {
    font-size: 30px;
    font-weight: 700;
    margin: 0;
}

.status-badge {
    padding: 6px 12px;
    border-radius: 999px;
    font-size: 0.9rem;
    font-weight: 700;
    border: 2px solid transparent;
}

.status-open {
    color: #0b7a50;
    background: #e8f5ee;
    border-color: #b6e3c9;
}

.status-closed {
    color: #0f0f0f;
    background: #f0f0f0;
    border-color: #0f0f0f;
}

/* Timeline */
.challenge-timeline {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    margin-top: 25px;
    gap: 20px;
    text-align: center;
    font-size: 17px;
}

.challenge-timeline [data-step] {
    padding: 12px 10px;
    border-radius: 12px;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.challenge-timeline strong {
    display: block;
    font-weight: bold;
}

.challenge-timeline span {
    display: inline-block;
    font-style: italic;
    margin-top: 5px;
    white-space: nowrap;
}

.challenge-timeline.single-row {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-top: 10px;
}

.challenge-timeline.single-row div {
    width: auto;
    white-space: nowrap;
}

.challenge-timeline.single-row strong {
    display: inline;
}

.challenge-timeline.single-row span {
    margin-top: 0;
    display: inline;
}


.challenge-timeline [data-step].is-active {
    background: #e6f2ff;
}

/* Progress Bar */
.challenge-progress {
    margin: 30px 0 10px;
}

.progress-bar {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    gap: 0;
    counter-reset: step;
    position: relative;
}

.progress-bar::before {
    content: '';
    position: absolute;
    top: 14px;
    left: 0;
    height: 3px;
    width: var(--progress-fill, 0%);
    background: #0074e0;
    transition: width 0.5s ease;
    z-index: 1;
}

.progress-bar li {
    flex: 1;
    position: relative;
    text-align: center;
    padding-top: 28px;
    font-size: 0.9rem;
    color: #4a5568;
}

.progress-bar li::before {
    counter-increment: step;
    content: '';
    width: 26px;
    height: 26px;
    border-radius: 50%;
    border: 3px solid #cfd8e3;
    background: #fff;
    display: block;
    margin: 0 auto 8px;
    transition: all 0.3s ease;
}

.progress-bar li::after {
    content: '';
    position: absolute;
    top: 14px;
    left: 50%;
    width: 100%;
    height: 3px;
    background: #e0e6ee;
    z-index: 0;
    transform: translateX(0);
}

.progress-bar li:last-child::after {
    display: none;
}

.progress-bar li span {
    display: block;
    font-weight: 700;
}

.progress-bar li.is-complete::before {
    background: #0074e0;
    border-color: #0074e0;
}

.progress-bar li.is-complete::after {
    background: #0074e0;
}

.progress-bar li.is-active::before {
    border-color: #00a9ff;
    background: #fff;
    box-shadow: 0 0 0 6px rgba(0, 169, 255, 0.18);
}

/* Description */
.challenge-description {
    font-size: 17px;
    line-height: 1.7;
    color: #333;
}

/* Join Link */
.challenge-link {
    display: inline-block;
    margin-top: 15px;
    font-size: 18px;
    color: #1c7c6c;
    text-decoration: none;
}

.challenge-link:hover {
    text-decoration: underline;
}

.challenge-actions {
    display: flex;
    gap: 12px;
    margin-top: 20px;
    flex-wrap: wrap;
}

.challenge-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 20px;
    border-radius: 999px;
    font-size: 16px;
    font-weight: 700;
    border: 2px solid #0b7a50;
    color: #0b7a50;
    background: #fff;
    text-decoration: none;
    transition: all 0.2s ease;
}

.challenge-btn:hover {
    background: #0b7a50;
    color: #fff;
    border-color: #0b7a50;
}

.challenge-btn.ghost {
    color: #0b7a50;
    background: #fff;
}

.challenge-btn.ghost:hover {
    color: #fff;
    background: #0b7a50;
    border-color: #0b7a50;
}

/* Responsive */
@media (max-width: 900px) {
    .challenge-timeline {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 500px) {
    .challenges-list {
        padding: 40px 20px;
    }

    .challenge-card {
        padding: 25px;
    }

    .challenge-timeline {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .challenge-card {
        width: 100%;
        padding: 22px;
        margin: 0 0 28px 0;
    }

    .challenge-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 6px;
    }

    .challenge-card h2 {
        font-size: 24px;
    }

    .countdown-timer {
        font-size: 0.85rem;
        padding: 6px 12px;
    }

    .progress-bar {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .progress-bar::before {
        display: none;
    }

    .progress-bar li {
        text-align: left;
        padding-top: 0;
        display: flex;
        align-items: center;
        gap: 10px;
    }

    .progress-bar li::after {
        display: none;
    }

    .progress-bar li::before {
        margin: 0;
    }
}