Use WAD to move, and S to crouch. You cannot attack while crouching. Each progressive wave of slimes will be harder than the last. Try to survive as long as you can!
*WORK IN PROGRESS* Thanks to @Yobo-Hobo and whomever @Yobo-Hobo may have borrowed scripts from. Also, thanks to Spelunky and Terraria for ideas on the weapons and slimes/music, respectively, and @Yobo-Hobo gave me inspiration for many new weapons, such as the AR, Grenades, and RPG.