Movement mechanics
The following are all the ways players can cover distance in Nightmare Reaper levels.
Always available
Apart from walking and jumping, of course.
Bunny Hopping
While running, jump as soon as you land, and the next jump will increase your horizontal speed. This effect stacks several times, and the first time you achieve its maximum level, you gain the "Bunny Hopper" achievement. Jump input is buffered, so you don't need to time it precisely, just holding it on landing is enough.
Weapon-based
Rocket Jumping
You can use any weapon with area of effect and self-damage to propel yourself away from the explosion. Jumping right before firing gives extra vertical speed, which helps cover significant height. Doing this 20 times earns you the "Burning Soles" achievement.
Chained Saw
The alternative attack of the Chained Saw shoots out a grappling hook that pulls you fast towards destination. While the chain isn't very long, its short cooldown allows you to travel without touching floor. This is the most popular way of cheesing challenge rooms.
Recoil Flying
Any weapon with recoil can be used simultaneously with jumping to make the jump higher. Even something as widespread as Sawed Off can give significant boost. A rapid fire weapon with strong enough "Kickback" stat is enough to achieve effective levitation.
Prone Position
There is no crouching bind in Nightmare Reaper, however, Machine Gun and Heavy Minigun allow player to go prone. Normal movement is drastically slowed in prone position, but the Chapter 2 grappling hook (see below) is still fully usable. It's possible to get into unintended areas using this.
Upgrades
Dash
Dash is a crucial movement ability which is unlocked as early as World 2 of Skill Tree. When activated, it instantly adds a significant momentum to player's horizontal speed. There are multiple upgrades for dash across Skill Tree and Jade Tree, both quantitive (like delay reduction and speed increase) and qualitative (like ability to dash in midair and ignoring monsters).
Dash jump
The action of dash is instant, and until World 5 of Skill Tree it can only be activated on the ground. Due to this, ground friction negates dash rather quickly. However, jumping right after activating dash allows you to save the bonus speed gained from the dash for the duration you spend airborne. This method drastically increases the distance you can cover by dashing.
Fun fact: It is known that this is ItBurn's personal favorite way of cheesing challenge rooms.
Double jump
World 4 of Skill Tree contains the upgrade that allows jumping in mid-air. Besides the obvious advantage of getting higher, it can be used to negate fall damage, or prolong duration of a dash jump.
Triple jump
World 8 of Skill Tree contains the upgrade that allows jumping twice in mid-air. This comes in handy when navigating some of the later Chapter 3 locations.
Ledge grabbing
TBD
Level features
Water pools
Found as early as Hollow Stone, bodies of water negate falling damage, thus making it easy to drop from heights. Using water to prevent falling damage in 50 instances earns the "Watch Your Step" achievement.
Jump pads
First introduced in Immemorial Woods, magic circles on the ground launch the protagonist in the air. The magic doesn't include fall protection. Beware that enemies are also able to take the shortcut.
Elevators
Starting with Sulfuric Mines, switch-operated elevators start appearing on the main path as a welcome counterpart to water pools to provide a fast way up.
Floating platforms
Found in Gloom Mansion, enchanted platforms move perpetually between two points. Unlike elevators, they can travel without connection to walls, and even through walls.
Accelerators
Starting with Void Beneath, this horizontal counterpart to jump pads makes an appearance. Notably, a combined variant is used in the last part of the Chapter 2 hub to access the Boulder Penitentiary.
Teleporters
Found in the Buried Ruins and the last hub exclusively, rune-activated obelisks connect two completely separate places. They maintain player's global orientation when entered.
Chapter progression
Grappling hook
At the beginning of Chapter 2, an unlimited-use grappling hook is found. Unlike the one chained to the saw, it has a separate binding, and can be used simultaneously with any weapons. There is only one limitation: it is dispelled over open water areas.
Red hook
At the beginning of Chapter 3, the hook is upgraded to allow traversal not just over open water, but also over nothing at all. It also travels faster and pulls stronger.