If you are looking to begin mapping, please start by reading the Basic Mapping page.
If you know the basics and are looking for a complete overview of all the important mapping topics, check the Intermediate Mapping page.
This page is a collection of individual detailed guides on specific topics from an advanced perspective and does not have a straightforward structure as the previous mapping pages. Feel free to skip around between the topics that interest you the most.
If you think you have some wisdom to share about something you are a master of, please consider contributing by modifying the existing pages or adding a new one.
If, while mapping, you notice that your song was properly aligned but suddenly changes or starts to fall off beat, then it's likely a BPM issue.
If the alignment suddenly and dramatically shifts for large parts of the song, but it seems consistent, it is likely your map has multiple BPMs. Depending on how often it occurs, this is relatively easy to fix. You can simply cut the map up into pieces where the grid becomes unaligned, and then run each one through Arrow Vortex to find the correct BPM for each part. You can then use BPM blocks to readjust the grid to align to the beat.
However, if the grid is less consistent and drifts around being aligned with no dramatic changes, then it is likely your song has a drifting BPM. This is common in older songs. This can be more of a hassle to deal with, but it is possible to address. Please see the variable BPM guide for more information.
There is knowledge written and discussed that is not completely included in the momentum section of the Intermediate Mapping page. However, nobody has yet spent the time presenting it in this page. For now, feel free to use what is written there.