style.css

body {
    --bg-color: hsla(220, 50%, 50%, 0.3);
    --border-color: hsla(220, 50%, 50%, 0.8);
    --header-text-color: hsla(0, 0%, 9.0196%, 1);
    --reg-text-color: hsla(0, 0%, 9.0196%, 1);
    --check-bg-color: hsla(40, 100%, 80%, 1);
    --check-bg-color-hover: hsla(40, 100%, 70%, 1);
    --delete-bg-color: hsla(40, 100%, 80%, 1);
    --delete-bg-color-hover: hsla(0, 50%, 50%, 1);
    --input-btn: hsla(40, 100%, 80%, 1);
    --input-btn-hover: hsla(40, 100%, 80%, 1);
    --input-bg-color: hsla(290, 50%, 95%, 1);
    --border-image: linear-gradient(var(--angle), hsla(220, 50%, 50%, 0.8))1;
    --err-box-bg: hsla(220, 50%, 50%, 0.8);
    --err-box-border: hsla(220, 50%, 30%, 0.9);
    --rgb-btn-bg: hsla(220, 50%, 80%, 1);
    --theme-btn-bg: hsla(220, 50%, 90%, 1);
}


.dark {
    --bg-color: hsla(240, 100%, 3%, 1);
    --border-color: hsla(240, 100%, 30%, 1);
    --header-text-color: hsla(240, 100%, 100%, 0.6);
    --reg-text-color: hsla(0, 30%, 5%, 1);
    --reg-text-hover: hsla(0, 0%, 50%, 1);
    --check-bg-color: hsla(40, 100%, 20%, 1);
    --check-bg-color-hover: hsla(40, 100%, 10%, 1);
    --delete-bg-color: hsla(240, 100%, 3%, 1);
    --delete-bg-color-hover: hsla(0, 100%, 10%, 1);
    --input-bg-color: hsla(290, 50%, 95%, 0.7);
    --border-image: linear-gradient(var(--angle), hsla(240, 100%, 30%, 1))1;
    --err-box-bg: hsla(240, 100%, 8%, 1);
    --err-box-border: hsla(240, 100%, 30%, 0.2);
    --rgb-btn-bg: hsla(220, 50%, 20%, 0.8);
    --theme-btn-bg: hsla(220, 50%, 50%, 1);


}

.rgb {
    --border-color: hsla(240, 100%, 8%, 0.1);
    --border-image: linear-gradient(var(--angle), red, green, blue)1;
}




/* Extra small devices (phones, 576px and down) */
@media only screen and (max-width: 576px) {
    * {
        --angle: 0deg;
        margin: 0;
        padding: 0;
        letter-spacing: 0.5px;
        box-sizing: border-box;
        transition: all ease-in-out .2s;
    }

    body {
        animation: 10s rotate linear infinite;
        background: var(--bg-color);
        position: relative;
        width: 100vw;
        height: 100vh;
        display: flex;
        flex-direction: column;
        align-self: center;
        justify-self: center;
        margin: auto;
        font-family: 'M PLUS Rounded 1c', sans-serif;
        transition: all ease-in-out .2s;

    }



    .btn-cont {
        display: flex;
        margin: 1rem 1rem;
        flex-wrap: wrap;
        transition: all ease-in-out .2s;
    }

    .btn-cont>button {
        /*padding: 4px 8px;*/
        padding: 3px 5px;
        margin: 0.2rem 0.1rem;

    }


    @keyframes rotate {
        to {
            --angle: 360deg;
        }
    }

    @property --angle {
        syntax: '<angle>';
        initial-value: 0deg;
        inherits: false;
    }


    .theme-toggler {
        background: var(--theme-btn-bg);
        margin-left: 1rem;
        transition: all ease-in-out .2s;
    }

    .reset-colors {
        display: none;
        margin-left: 8px;
    }

    .random-color-btn {
        margin-left: auto;
    }

    .undoBtn {
        padding: 4px 8px;
        margin-left: 8px;
    }



    .rgb-toggler {
        background: var(--rgb-btn-bg);
        margin-left: 8px;
        transition: all ease-in-out .2s;

    }

    .rgb-toggler:hover {
        background: var(--rgb-btn-bg);
        background: linear-gradient(var(--angle), red, green, blue);
        transition: all ease-in-out .2s;


    }

    .add-task {
        margin-left: 100vw;
    }

    .container {
        height: 100%;
        overflow: scroll;
        transition: all ease-in-out .2s;
    }

    .heading-h2 {
        display: flex;
        font-size: 1.3rem;
        justify-content: center;
        align-items: center;
        padding: 20px;
        text-align: center;
        margin: 0;
    }

    .task.task-margin {
        margin-bottom: 2rem;
    }

    .task {

        margin-bottom: 1rem;
        display: flex;
    }

    .add-task-container {
        transition: all ease-in-out .2s;
        margin: 0 1rem;
    }

    .deleteTask:hover {
        background: var(--delete-bg-color-hover);
    }



    .err-message {
        display: none;
        height: auto;
        justify-content: center;
        align-items: center;
        padding: 20px;
        margin: 1rem;
        background-color: var(--err-box-bg);
        border-radius: 10px;
        color: white;
        text-align: center;
        border: 3px solid var(--err-box-border);
        border-image: var(--border-image);
        font-size: 1rem;
        font-weight: 400;
        letter-spacing: 1px;
        transition: all ease-in-out .2s;

    }



    h1 {
        padding: 20px;
        color: var(--header-text-color);
        text-align: center;
        font-size: 1.6rem;
        text-decoration-line: underline;
        text-decoration-color: hsla(330, 100%, 50%, 1.0);

    }

    .movie-wrapper,
    form,
    h1 {
        display: flex;
        align-items: center;
        justify-content: center;
        transition: all ease-in-out .2s;

    }


    .li-and-remove-btn-wrapper {
        display: flex;
        align-items: center;
        justify-content: center;
        width: 100vw;
        letter-spacing: 0.5px;
        margin: 1rem 1rem;
        transition: all ease-in-out .2s;

    }

    .movie-wrapper {

        background: hsla(220, 50%, 50%, 0.4);
        padding: 20px 5px;
        border-bottom: 1px solid hsla(220, 50%, 50%, 0.8);
        display: flex;
        flex-direction: column;
        align-items: center;
        height: auto;
        transition: all ease-in-out .2s;
        justify-content: space-between;
    }

    button:last-child:not(.undoBtn) {
        letter-spacing: 0.5px;
        transition: all ease-in-out .2s;
        margin-left: 0.1rem;
    }

    button {
        background: var(--check-bg-color);
        font-size: 0.8rem;
        transition: all ease-in-out .2s;
        position: relative;
        color: var(--reg-text-color);
        padding: 7px 11px;
        border: 3px solid var(--border-color);
        border-image: var(--border-image);
        letter-spacing: 0.5px;
        border-radius: 10px;
        border-radius: 10px !important;
        animation: 10s rotate linear infinite;

    }

    button:hover {
        background: var(--check-bg-color-hover);
        color: var(--reg-text-hover);
        transition: all ease-in-out .2s;


    }



    form button:hover {
        background: hsla(60, 100%, 99%, 1);

    }

    form button:active {
        background: hsla(220, 100%, 20%, 1);

    }

    li {
        border: 3px solid var(--border-color);
        text-decoration-style: none;
        list-style-type: none;
        padding: 7px 11px;
        transition: all ease-in-out .2s;
        animation: 10s rotate linear infinite;
        border-radius: 10px;
        font-size: 0.8rem;
        background: var(--input-bg-color);
        border-image: var(--border-image);
        letter-spacing: 0.5px;
        margin-right: auto;

    }

    form {
        background: hsla(220, 50%, 50%, 0.7);
        padding: 30px 0;
        border-bottom: 1px solid blue;
        display: flex;
        align-items: center;
        justify-content: center;
        transition: all ease-in-out .2s;

    }

    img {
        font-size: 1.4rem;
        border: 3px solid hsla(220, 50%, 50%, 1);
    }


    input {
        background: var(--input-bg-color);
        transition: all ease-in-out .2s;
        font-size: 0.8rem;
        padding: 15px 10px;
        width: 100%;
        border: 3px solid var(--border-color);
        border-image: var(--border-image);
        border-radius: 10px;
        overflow: hidden;
        animation: 10s rotate linear infinite;
    }

    input:focus-within {
        color: hsla(220, 80%, 20%, 1);
        letter-spacing: 0.5px;
    }

    input:focus-visible {
        outline: 3px solid white;
        border-radius: 12px;
    }
}


/* Small devices (portrait tablets and large phones, 576px and up) */
@media only screen and (min-width: 576px) {

    * {
        --angle: 0deg;
        margin: 0;
        letter-spacing: 0.5px;
        padding: 0;
        box-sizing: border-box;
        transition: all ease-in-out .2s;
    }

    body {
        background: var(--bg-color);

        animation: 10s rotate linear infinite;
        position: relative;
        width: 80vw;
        height: 100vh;
        display: flex;
        flex-direction: column;
        align-self: center;
        justify-self: center;
        margin: auto;
        font-family: 'M PLUS Rounded 1c', sans-serif;
        transition: all ease-in-out .2s;

    }

    input:focus-visible {
        outline: 3px solid white;
        border-radius: 12px;
    }

    .btn-cont {
        display: flex;
        margin: 1rem 1rem;
        transition: all ease-in-out .2s;
    }

    .btn-cont>button {
        transition: all ease-in-out .2s;
        padding: 4px 8px;
    }


    @keyframes rotate {
        to {
            --angle: 360deg;
        }
    }

    @property --angle {
        syntax: '<angle>';
        initial-value: 0deg;
        inherits: false;
    }

    .theme-toggler {
        background: var(--theme-btn-bg);
        margin-left: 8px;
        transition: all ease-in-out .2s;
    }

    .reset-colors {
        display: none;
        margin-left: 8px;
    }

    .random-color-btn {
        margin-left: auto;
    }

    .undoBtn {
        padding: 4px 8px;
        margin-left: 1rem;
        transition: all ease-in-out .2s;

    }

    .rgb-toggler {
        background: var(--rgb-btn-bg);
        margin-left: 1rem;
        transition: all ease-in-out .2s;

    }

    .rgb-toggler:hover {
        background: var(--rgb-btn-bg);
        background: linear-gradient(var(--angle), red, green, blue);
        transition: all ease-in-out .2s;

    }

    .add-task {
        margin-left: 100vw;
    }

    .container {
        height: 100%;
        overflow: scroll;
        transition: all ease-in-out .2s;
    }

    .heading-h2 {
        display: flex;
        font-size: 1.3rem;
        justify-content: center;
        align-items: center;
        padding: 20px;
        text-align: center;
        margin: 0;
    }

    .task.task-margin {
        margin-bottom: 2rem;
    }

    .task {

        margin-bottom: 1rem;
        display: flex;
    }

    .add-task-container {
        margin: 0 1rem;
        transition: all ease-in-out .2s;
    }

    .deleteTask:hover {
        background: var(--delete-bg-color-hover);
    }

    button:last-child:not(.undoBtn) {
        margin-left: 0.5rem;
    }

    .err-message {
        display: none;
        height: auto;
        justify-content: center;
        align-items: center;
        padding: 20px;
        margin: 6rem;
        background-color: var(--err-box-bg);
        border-radius: 10px;
        color: white;
        text-align: center;
        border: 3px solid var(--err-box-border);
        border-image: var(--border-image);
        font-size: 1rem;
        font-weight: 400;
        letter-spacing: 1px;
        transition: all ease-in-out .2s;

    }



    h1 {
        padding: 20px;
        color: var(--header-text-color);
        text-align: center;
        font-size: 1.6rem;
        text-decoration-line: underline;
        text-decoration-color: hsla(330, 100%, 50%, 1.0);

    }

    .movie-wrapper,
    form,
    h1 {
        display: flex;
        align-items: center;
        justify-content: center;
        transition: all ease-in-out .2s;

    }


    .li-and-remove-btn-wrapper {
        display: flex;
        align-items: center;
        justify-content: center;
        width: 100vw;
        margin: 1rem 1rem;
        transition: all ease-in-out .2s;

    }

    .movie-wrapper {

        background: hsla(220, 50%, 50%, 0.4);
        padding: 20px 5px;
        border-bottom: 1px solid hsla(220, 50%, 50%, 0.8);
        display: flex;
        flex-direction: column;
        align-items: center;
        height: auto;
        transition: all ease-in-out .2s;
        justify-content: space-between;
    }

    button {
        background: var(--check-bg-color);
        font-size: 0.8rem;
        transition: all ease-in-out .2s;
        position: relative;
        color: var(--reg-text-color);
        padding: 7px 11px;
        border: 3px solid var(--border-color);
        border-image: var(--border-image);
        border-radius: 10px;
        border-radius: 10px !important;
        overflow: hidden;
        animation: 10s rotate linear infinite;

    }

    button:hover {
        background: var(--check-bg-color-hover);
        color: var(--reg-text-hover);
        transition: all ease-in-out .2s;


    }

    form button:hover {
        background: hsla(60, 100%, 99%, 1);

    }

    form button:active {
        background: hsla(220, 100%, 20%, 1);

    }

    li {
        border: 3px solid var(--border-color);
        text-decoration-style: none;
        list-style-type: none;
        padding: 7px 11px;
        transition: all ease-in-out .2s;
        animation: 10s rotate linear infinite;
        border-radius: 10px;
        font-size: 0.8rem;
        background: var(--input-bg-color);
        letter-spacing: 0.5px;
        border-image: var(--border-image);
        margin-right: auto;

    }

    form {
        background: hsla(220, 50%, 50%, 0.7);
        padding: 30px 0;
        border-bottom: 1px solid blue;
        display: flex;
        align-items: center;
        justify-content: center;
        transition: all ease-in-out .2s;

    }

    img {
        font-size: 1.4rem;
        border: 3px solid hsla(220, 50%, 50%, 1);
    }

    input:focus-within {
        color: hsla(220, 80%, 20%, 1);
        letter-spacing: 0.5px;
    }


    input {
        background: var(--input-bg-color);
        transition: all ease-in-out .2s;
        font-size: 0.8rem;
        padding: 15px 10px;
        width: 100%;
        border: 3px solid var(--border-color);
        border-image: var(--border-image);
        border-radius: 10px;
        animation: 10s rotate linear infinite;
    }

}


/* Medium devices (landscape tablets, 768px and up) */
@media only screen and (min-width: 768px) {
    body {
        background: var(--bg-color);
        letter-spacing: 0.5px;
        width: 60vw;
    }
}

/* Large devices (laptops/desktops, 992px and up) */
@media only screen and (min-width: 992px) {
    body {
        background: var(--bg-color);
        letter-spacing: 0.5px;
        width: 50vw;
    }
}