In the earliest builds (pre-Act 2), the slide physics were significantly more volatile. The "Slide Coasting" (preserving momentum infinitely) was initially considered a bug by the developer, Hakita.
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V1’s slide is activated by holding the (typically Left Ctrl ) while on the ground. Unlike many games where sliding has a fixed duration, V1 can slide indefinitely as long as you hold the key and have enough speed. v1 slide ultrakill