/* allgemeine Konfigurationen */
:root {
	--size: 50px;
	--font-size: 40px;
	--outer-border-width: 3px;
	--inner-border-width: 1px;
	--page-width: 500px;
}

body {
	background: yellow;
	font-family: arial;
	font-weight: 300;
	margin: 0;
}

header {
    background: #222;
}

.h1 {
	font-size: 35;
	text-align: center;
	color: #ffffff;
}

.sudokubild {
    width: 20%;
}

main {
	width: var(--page-width);
	margin: 0 auto;
}

/* festes Feld; Wert kann nicht geändert werden */
input.fixed {
	background: lightgrey;
	color: black;
}

input[type="submit"], button {
	display: block;
	width: 70%;
	height: 40px;
	margin: 10px 0;
	font-size: 20px;
	border: solid 1px #00e300;
	background: #f0f0f0;
}

input[type="submit"]:hover, input[type="submit"]:focus, button:hover, button:focus {
	border: solid 3px #2E64FE;
    background: #dcd8d8;
}

#sudoku {
	display: inline-block;
}

/* aussehen eines Feldes */
.input {
	margin: 0;
	width: var(--size);
	height: var(--size);
	line-height: var(--size);
	font-size: var(--font-size);
	text-align: center;
	border: solid var(--inner-border-width) grey;
	display: inline-block;
	position: relative;
	overflow: hidden;
	float: left;
}

/* Input-Felder zentrieren */
.input input {
	position: absolute;
	top: 0;
	bottom: 0;
	left: 0;
	right: 0;
	border: none;
	width: var(--size);
	height: var(--size);
	font-size: var(--font-size);
	text-align: center;
}

/* Input-Feld, in dem ein Buchstabe oder ungültiges Zeichen steht */
.input input:invalid {
    background: darkred;
}

/* nach 9 Feldern 'umbrechen' (wieder vorne anfangen)
	dickerer Strich auf der linken Seite */
.input:nth-child(9n+1) {
	clear: left;
	border-left: solid var(--outer-border-width) grey;
}

/* dickerer Strich nach 3 Feldern (wagerecht) */
.input:nth-child(n+19):nth-child(-n+27),
.input:nth-child(n+46):nth-child(-n+54),
.input:nth-child(n+73):nth-child(-n+81) {
    border-bottom: solid var(--outer-border-width) grey
}

/* dickerer Strich nach drei Feldern (senkrecht) */
.input:nth-child(3n) {
    border-right: solid var(--outer-border-width) grey
}

/* dickerer Strich oberhalb des Feldes */
.input:nth-child(n+1):nth-child(-n+9) {
    border-top: solid var(--outer-border-width) grey
}

.erklärung {
    font-size: 30;
    color: #2E64FE;
    text-align: center;
    font-weight: bold;
}

input[id="neustarten"]:hover, input[id="neustarten"]:focus, button:hover, button:focus {
	border: solid 3px #2E64FE;
    background: #dcd8d8;
}

.einstellungen {
    background: #222;
    font-size: 50;
    color: #ffffff;
    text-align: center;
    font-weight: bold;
    margin: 0;
    padding: 0;
    height: 60px;
    }

input[type="submit"][name="absenden"], button {
	display: block;
	width: 10%;
	height: 40px;
	margin: 10px 0;
	font-size: 20px;
	border: solid 1px #00e300;
	background: #f0f0f0;
}

input[name="absenden"]:hover, input[name="absenden"]:focus, button:hover, button:focus {
	border: solid 3px #2E64FE;
        background: #dcd8d8;
}

input[type="submit"][name="richtig"], button {
	display: block;
	width: 15%;
	height: 40px;
	margin: 10px 0;
	font-size: 20px;
	border: solid 1px #00e300;
	background: #f0f0f0;
}

input[name="richtig"]:hover, input[name="richtig"]:focus, button:hover, button:focus {
	border: solid 3px #2E64FE;
        background: #dcd8d8;
}