--- /dev/null
+/* We want our board to be the largest square that can
+ * fit. Unfortunately, it requires a bit of CSS magic to make that
+ * happen. We can set a width easily enough, but what we can't easily
+ * do is to set the height to be exactly the same as the width.
+ *
+ * So here's the magic to get that to happen. On the board container
+ * we set the height to 0 and the bottom padding to 100% (which just
+ * happens to be defined as relative to the _width_). So, now we have
+ * a square element. Hurrah!
+ *
+ * The problem is that this element has a nominal height of 0, so if
+ * any child sas "height: 100%" that will result in a 0-height child
+ * and won't be what we want.
+ *
+ * So the last piece of the magic is to use absolute placement of the
+ * board (which requires position:relative on its parent) and set all
+ * of its edges (top, left, bottom, right) to the extents of the
+ * container.
+ *
+ * Ta-da! Now our board element is square and does not have any
+ * dimensions of 0 so child elements can compute their sizes
+ * naturally.
+ */
+.board-container {
+ position: relative;
+ width: 100%;
+ height: 0;
+ padding-bottom: 100%;
+}
+
+.board {
+ position: absolute;
+ top: 0;
+ left: 0;
+ bottom: 0;
+ right: 0;
+
+ display: grid;
+ grid-template-columns: 1fr 1fr 1fr;
+ grid-template-rows: 1fr 1fr 1fr;
+ grid-gap: 1em;
+}
+
+.mini-grid {
+ width: 100%;
+ height: 100%;
+
+ display: grid;
+ grid-template-columns: 1fr 1fr 1fr;
+ grid-template-rows: 1fr 1fr 1fr;
+
+ border-radius: 6px;
+ border: 3px solid #999;
+}
+
+.mini-grid.active {
+ border: 3px solid var(--accent-color-bright);
+}
+
+.square {
+ display: flex;
+ justify-content: center;
+ align-items: center;
+ font-size: calc(min(8vw, .08 * var(--page-max-width)));
+ line-height: 0;
+ font-weight: bold;
+ border-bottom: 1px solid #999;
+ border-right: 1px solid #999;
+}
+
+.square.open {
+ cursor: pointer;
+}
+
+.square.occupied {
+ cursor: default;
+}
+
+.square.open:hover {
+ background-color: var(--accent-color-bright);
+}
+
+.square.last-move {
+ color: var(--accent-color-bright);
+}
+
+.glyphs {
+ padding-top: 0.5em;
+ display: grid;
+ grid-template-columns: 1fr 1fr 1fr 1fr 1fr;
+ grid-column-gap: 0.5em;
+ grid-row-gap: 0.25em;
+}
+
+.glyph-and-name {
+ display: flex;
+ flex-direction: column;
+ align-items: center;
+}
+
+.glyph {
+ width: 8vw;
+}