The best alternatives to Snake Next are Snake '97, Yeti run for SkiFree, and JustSnake. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Snake Next?
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SnakeLogic is an interesting snake game, 30 levels with increasing difficulty. You have to figure it out yourself how to progress. :) Level creator is included so levels can be added as well. Some levels need just navigate the snake others levels need strong puzzle solving and strategic skills.