* {
    margin: 0;
    padding: 0;
    font-family: 'Poppins', sans-serif;
    box-sizing: border-box;
}
.container {
    width: 100%;
    min-height: 100vh;
    background: linear-gradient(135deg, #151511, #1f288a);
    padding: 10px;
}
.todo-app {
    width: 100%;
    max-width: 540px;
    background: #fff;
    margin: 100px auto 20px;
    padding: 40px 30px 70px;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}
.todo-app h2 {
    color: #002765;
    display: flex;
    align-items: center;
    margin-bottom: 20px;
}
.todo-app h2 img {
    width: 30px;
    margin-left: 10px;
}
.row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #eed;
    border-radius: 30px;
    padding-left: 20px;
    margin-bottom: 25px;
}
input {
    flex: 1;
    border: none;
    outline: none;
    background: transparent;
    padding: 10px;
    font-size: 16px;
}
button {
    outline: none;
    border: none;
    padding: 16px 50px;
    background-color: #ee2354;
    font-size: 16px;
    cursor: pointer;
    color: #d1c9c9;
    border-radius: 40px;
}
ul li {
    list-style: none;
    font-size: 17px;
    padding: 12px 8px 12px 50px;
    user-select: none;
    cursor: pointer;
    position: relative;
}
ul li::before {
    content: '';
    position: absolute;
    height: 28px;
    border-radius: 50%;
    width: 28px;
    background-image: url(images/unchecked.png);
    background-size: cover;
    background-position: center;
    top: 12px;
    left: 8px;
}
ul li.checked {
    color: #555;
    text-decoration: line-through;
}
ul li.checked::before {
    background-image: url(images/checked.png);
}
ul li span {
    position: absolute;
    right: 0;
    top: 5px;
    width: 40px;
    height: 40px;
    font-size: 22px;
    color: #555;
    line-height: 40px;
    text-align: center;
    border-radius: 50%;
}
ul li span:hover {
    background: #5a73a5;
}
#btn {
    background-color: #240909;
    display: block;
    margin: auto;
    justify-content: center;
    padding: 20px;
}

/* Media Queries */
@media (max-width: 768px) {
    .todo-app {
        padding: 30px 20px 60px;
    }
    button {
        padding: 12px 30px;
    }
    ul li {
        font-size: 16px;
        padding: 10px 8px 10px 40px;
    }
    ul li::before {
        height: 24px;
        width: 24px;
        top: 10px;
        left: 6px;
    }
    ul li span {
        width: 35px;
        height: 35px;
        font-size: 20px;
        top: 3px;
    }
}

@media (max-width: 480px) {
    .todo-app {
        padding: 20px 15px 50px;
    }
    .todo-app h2 {
        flex-direction: column;
        align-items: flex-start;
    }
    .todo-app h2 img {
        margin-left: 0;
        margin-top: 10px;
    }
    .row {
        flex-direction: column;
        align-items: flex-start;
        padding-left: 10px;
    }
    input {
        font-size: 14px;
        padding: 8px;
    }
    button {
        padding: 10px 20px;
        font-size: 14px;
    }
    ul li {
        font-size: 15px;
        padding: 8px 8px 8px 35px;
    }
    ul li::before {
        height: 20px;
        width: 20px;
        top: 8px;
        left: 4px;
    }
    ul li span {
        width: 30px;
        height: 30px;
        font-size: 18px;
        top: 2px;
    }
}