Examples: Fix floor threshold in `games_fps`. (#33053)

examples/games_fps.html

@@ -203,7 +203,9 @@
 
 				if ( result ) {
 
-					playerOnFloor = result.normal.y > 0;
+					// determine if the surface we bumped into is something we can stand on
+
+					playerOnFloor = result.normal.y >= 0.15; // allow slopes up to ~81° but ignore sheer vertical walls
 
 					if ( ! playerOnFloor ) {