Horizontal and vertical are orthogonal axes. Don’t add force in the one you don’t want acceleration to occur in.
Otherwise, if that’s not your question, how to report your problem productively in the Unity3D forums:
This is the bare minimum of information to report:
- what you want
- what you tried
- what you expected to happen
- what actually happened, especially any errors you see
- links to documentation you used to cross-check your work (CRITICAL!!!)
If you post a code snippet, ALWAYS USE CODE TAGS:
How to use code tags: Using code tags properly
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