.project-challenges {
    background: #1A1A1A; /* nền đen */
    border-radius: 20px;
    padding: 80px 20px;
    margin: 60px auto;
    max-width: 1170px;
    color: #fff; /* mặc định chữ trắng */
    position: relative;
    overflow: hidden;
    box-shadow: 0 10px 25px rgba(0,0,0,0.4);
    font-family: "Montserrat", sans-serif;
}

.project-container {
    display: flex;
    gap: 50px;
    align-items: flex-start;
    flex-wrap: wrap;
}

/* Left cards */
.challenges-list {
    flex: 1;
    max-height: 500px;
    overflow-y: scroll;
    padding-right: 10px;
    scroll-behavior: smooth;
    scrollbar-width: none;
    -ms-overflow-style: none;
    position: relative;
}

    .challenges-list::-webkit-scrollbar {
        display: none;
    }

    .challenges-list::after {
        content: "";
        position: absolute;
        bottom: 0;
        left: 0;
        right: 0;
        height: 40px;
        background: linear-gradient(to bottom, rgba(26,26,26,0), #1A1A1A);
        pointer-events: none;
    }

.challenge-card {
    background: #2a2a2a; /* card xám đậm nổi trên nền đen */
    color: #eee;
    padding: 25px 20px;
    border-radius: 15px;
    border: 2px solid #D4A017; /* viền vàng */
    box-shadow: 0 4px 10px rgba(0,0,0,0.4);
    margin-bottom: 20px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    cursor: default;
}

    .challenge-card img {
        width: 50px;
        margin-bottom: 15px;
        filter: brightness(0) invert(1); /* icon trắng trên nền tối */
    }

    .challenge-card h3 {
        font-size: clamp(16px, 2vw, 20px);
        font-weight: 700;
        margin-bottom: 8px;
        color: #D4A017; /* vàng nổi bật */
    }

    .challenge-card p {
        font-size: clamp(13px, 1.5vw, 15px);
        line-height: 1.5;
        color: #ccc;
    }

    .challenge-card:hover {
        transform: translateY(-5px);
        box-shadow: 0 8px 18px rgba(0,0,0,0.6);
    }

/* Right intro */
.challenge-intro {
    flex: 1;
    min-width: 300px;
    transition: all 0.6s ease;
}

    .challenge-intro h2 {
        font-size: clamp(22px, 4vw, 32px);
        font-weight: 800;
        margin-bottom: 20px;
        line-height: 1.3;
        color: #fff;
    }

        .challenge-intro h2 span {
            color: #D4A017; /* nhấn mạnh vàng */
        }

    .challenge-intro p {
        font-size: clamp(15px, 2vw, 16px);
        margin-bottom: 30px;
        color: #ddd;
        opacity: 0.95;
    }

.btn-findout {
    display: inline-block;
    padding: 12px 22px;
    border-radius: 30px;
    background: #D4A017; /* nút vàng */
    color: #111;
    font-weight: 600;
    text-decoration: none;
    transition: 0.3s;
}

    .btn-findout:hover {
        background: #b98a13;
        color: #fff;
    }

/* Tablet */
@media (max-width: 991px) {
    .project-container {
        flex-direction: column;
        text-align: center;
        gap: 30px;
    }

    .challenge-intro {
        order: -1;
    }

    .challenges-list {
        max-height: 350px;
        overflow-y: auto;
        padding-right: 5px;
    }

    .challenge-card {
        margin: 0 auto 20px auto;
        max-width: 500px;
    }
}

/* Mobile */
@media (max-width: 767px) {
    .project-challenges {
        padding: 50px 15px;
        margin: 40px auto;
    }

    .btn-findout {
        padding: 10px 18px;
        font-size: 15px;
    }
}

/* Mobile nhỏ */
@media (max-width: 480px) {
    .challenge-card img {
        width: 40px;
    }
}