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Note 2 - Summary of Significant Accounting Policies - Assumptions Used to Estimate the Fair Value of the Forward Liability (Details)	Sep. 30, 2021
Fair Value of Underlying Security [Member] | Valuation, Income Approach [Member]
Forward liability	2.65

X

- Definition

Value of input used to measure derivative liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_DerivativeLiabilityMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_MeasurementInputTypeAxis=bysi_FairValueOfUnderlyingSecurityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_IncomeApproachValuationTechniqueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: