Scroll down for instructions.
The player is designed to fit a standard 4:3 video monitor. If you have a wide-screen monitor then you may need to zoom in so that the player fits your screen width. Open one of the sites and look for an interesting video to play. Do not open the video page. Just right-click to copy the link and then paste it in the Alleycat Player input line. Press the "Play Video" button and your video should play. You can select the desired resolution (360p, 480p, 720p). Note that the actual resolution may not match your selection. When the video starts, the resolution will be shown in the box next to the input line. You can press "Clear" to clear the viewer. Press "Copy Link" if you wish to copy the link to the clipboard so that you can play the video in VLC or SMPlayer or whatever.
If you like what you see then go here for the real thing.