Samus will retain the speed booster while holding the direction she is travelling on the ground and serval actions for platforming. This trick is heavily cooperated with instantspark.
To understand the mechanics more clearly, we must know that there are three states of the speedboost (beware that these are not offically named):
Activated Speedboost, Charged Shinespark, Remaining Speedboost
Activated Speedboost state is when you finish your charging after running 17 tiles. Samus will glow in light-blue with her boost active and leaving lighting from her steps. Majorly, her speed increases. Samus in this state can only run into the direction she is facing or else the state will break. You can keep the state even from the action of morphing, jumping, sliding. However, the action of meleeing, free aiming, flash shifting, activate cloak will return Samus back to her normal state.
Charged Shinespark state is when Samus pull the direction down in the Activated Speedboost state. Smaus will glow in purple. In this state, Samus can perform actions of flash shift and free romming like without the speedboost active but this state only lasts for 5 seconds. When pressing B without direction in this state, samus will starting charging up and can propel herself in 8 direction. This also works the same way when instantsaprking. Please look into the page for more details.
Remaining Speedboost state is when Samus running off a ledge or Unmorphing midair in the Activated Speedboost state. Samus' constantly glowing blue is more obvious and the booster on the back shut down. In this state, Samus cannot space jump and landing will cause the speedboost state ends. You can enter Charge Shinespark state if you input a downward direction and having the Remaining Speedboost state.
Topography that majorly connected to the speedboost mechanics. When Samus shinespark toward a ledge with a horizontal direction. Samus will revert back to her Activated Speedboost state no matter the angle of the slope. Furthermore, sparking toward it without direction input will bonk if you are the same level or you got push up if you just under a few pixels at the top.
For slope ceilings, you will got blocked or pushed down if the slope has space under it. Strangely enough, you will get pushed and forcefully morph if the slope is connecting to a one tile space and Samus is spark on the same level of the floor.
slope_ceiling_spark.mp4
Samus can bring the speedboost up to 4 tile high platfroms and even 5 tile high with a precise midair morph.
At the adjacent of the ledge, you can slide and morph off the ledge to keep the speedboost state. If you press the ZL button late, Samus will morph instead slide but the state will remain. Moreover, the timing of slide morph have different outcomes
When Samus is falling in human form while hitting a ledge, Samus will grab onto the ledge, breaking the speedboost. You can avoid this by releasing direction input or morphing which cause samus to fall pass the ledge and keeping the boost.
Unlike previous titles, Samus can wall jump and retain the speedboost state. When Samus wall jump, her direction will alter to the opposite. The window of you can redirect the direction input is quite short that you should input the direction immediately after you press B for wall jumpping. Alternative solution, you can release your direction stick to neutral when jumping. Then you just input direction whenever you needed. Furthermore, same as wall jumpping, the bigger the jump. The more height gain momentum Samus will have. In other words, you can perform a double jump with speed in narrow spaces.
The time of Samus touching the wall and retaining the state seems to according to the falling momentum of Samus. Therefore, it's easy to lose speedboost if you are falling but jumping against the wall has a observable, longer time that can hold almost a second.
You can also perform a similar trick that alike single wall jump, shorten the wall jump distance via morphing. Then unmorph to enter Remained Speedboost state which helps resulting unnesscary yet cool speedkeeps.
Morph tunnels have a odd interaction with the speedboost. If you morph jump out of the tunnel, you cannot keep the Activated Speedboost state and only store the shinespark. On the other hand, the Ghavoran speedkeep can keep the Activated Speedboost state. The general solution is to bonk the ceiling near the end to land outside instead free falling.