The easiest, safest and best way to download games for offline use from itch is to use the official itch app from https://itch.io/app which works on PC. Then easiest way to find this game would be to copy this webpage https://gamefavorites.itch.io/arrow-sequence and paste it into the itch app search bar. Then when it loads up, click on the cog and click on install. It should then appear in your library with any other games you want to download