A little late here but I finally released a free downloadable demo for Slime Slam. The demo includes only Endless Mode, but all the customization features are present and there is no time limit on play. Hopefully this will get people to try the game out and see if they like it before purchasing.
The demo is also playable with 2 players, though Versus mode is locked, the side-by-side feature of Endless mode is present.