:root {
    --color-primary: #4b8150;
    --color-primary-rgb: 75, 129, 80;
    --color-primary-dark: #38613c;
    --color-primary-dark-rgb: 56, 97, 60;
    --color-white: #e7e4e7;
    --color-white-rgb: 231, 228, 231;
    --color-text: #474847;
    --color-text-rgb: 71, 72, 71;
}
::selection {
    color: var(--color-white);
    background-color: var(--color-primary-dark);
}

a:link,
a:visited {
    color: inherit;
}

html {
    box-sizing: border-box;
    font-size: 16px;
    font-family:
        Seravek, 'Gill Sans Nova', Ubuntu, Calibri, 'DejaVu Sans',
        source-sans-pro, sans-serif;
    min-height: 100vh;
}

*,
*:before,
*:after {
    box-sizing: inherit;
}

body,
h1,
h2,
h3,
h4,
h5,
h6,
p,
ol,
ul {
    margin: 0;
    padding: 0;
    font-weight: normal;
}

ol,
ul {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
}

body {
    background: var(--color-white);
    min-height: 100vh;
    color: var(--color-text);
}

.app {
    display: flex;
    flex-direction: column;
    width: 100%;
    max-width: 32em;
    min-height: 100vh;
    margin: 0 auto;
    padding: 1em;
    justify-content: center;
    align-content: stretch;
}

.header__logo {
    display: block;
    margin: 0 auto;
    width: 100%;
    height: 4.8em;
    background: transparent url('/favicon.svg') no-repeat center center;
    background-size: contain;
}
.header__title {
    display: block;
    text-align: center;
    margin: 0.4em 0 0.8em;
    font-size: 2.1em;
    font-weight: bold;
}

.todo {
    position: relative;
    margin-bottom: 2.4em;
    padding: 0 0 0 4.2em;
}
.todo:not(:last-child):after {
    content: '';
    position: absolute;
    inset: 0 auto -2.4em 1.3em;
    width: 0.2em;
    background: rgba(var(--color-primary-rgb), 0.1);
    z-index: -2;
}
.todo__number {
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    width: 2.4em;
    height: 2.4em;
    line-height: 2.4em;
    border-radius: 1.2em;
    text-align: center;
    font-size: 1.2em;
    font-weight: bold;
    user-select: none;
    background: rgba(var(--color-primary-rgb), 0.15);
    color: var(--color-primary);
}
.todo__number:before {
    content: '';
    position: absolute;
    top: -0.5em;
    left: -0.5em;
    width: 3.4em;
    height: 3.4em;
    border-radius: 1.7em;
    background: var(--color-white);
    z-index: -1;
}
.todo__title {
    padding: 0.5em 0 0.2em;
    line-height: 1.4em;
    font-size: 1.2em;
    font-weight: bold;
    opacity: 0.8;
}

.button {
    display: inline-block;
    margin: 0.8em 0 0;
    padding: 0.6em 1.2em;
    border-radius: 0.6em;

    font: inherit;
    color: var(--color-white);
    background: var(--color-primary);
    border: none;
    outline: none;

    cursor: pointer;
}
.button:not(.button--ok):not(:active):hover {
    box-shadow: 0 0 1.2em rgba(0, 0, 0, 0.1);
}
.button:active,
.button--ok {
    box-shadow: 0 0 1.2em rgba(0, 0, 0, 0.2);
    background: var(--color-primary-dark);
}
.button--ok {
    pointer-events: none;
    color: transparent;
    background: var(--color-primary)
        url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" stroke-width="2" stroke="white" fill="none" stroke-linecap="round" stroke-linejoin="round"><path stroke="none" d="M0 0h24v24H0z" fill="none"></path><path d="M5 12l5 5l10 -10"></path></svg>')
        center center no-repeat;
}

.footer {
    margin: 4.8em 0 0;
}
.footer__text {
    text-align: center;
    font-size: 0.8em;
    margin: 0;
    opacity: 0.6;
}