Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at the beginning of the period (in shares) at Dec. 31, 2019	20,998,000
Balance at the beginning of the period at Dec. 31, 2019	$ 173,068
Redeemable Convertible Preferred Stock
Issuance upon exercise of warrants (in shares)	75,000
Issuance upon exercise of warrants	$ 379
Balance at the end f the period (in shares) at Mar. 31, 2020	21,073,000
Balance at the end of the period at Mar. 31, 2020	$ 173,447
Balance at the beginning of the period (in shares) at Dec. 31, 2019		2,290,000
Balance at the beginning of the period at Dec. 31, 2019	(143,837)	$ 0	$ 4,808	$ 4	$ (148,649)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of vested options (in shares)		602,000
Issuance upon exercise of options	1,024		1,024
Stock-based compensation expense	561		561
Unrealized loss on cash equivalents	(7)			(7)
Net loss	(13,126)				(13,126)
Balance at the end of the period (in shares) at Mar. 31, 2020		2,892,000
Balance at the end of the period at Mar. 31, 2020	$ (155,385)	$ 0	6,393	(3)	(161,775)
Balance at the beginning of the period (in shares) at Dec. 31, 2019	20,998,000
Balance at the beginning of the period at Dec. 31, 2019	$ 173,068
Balance at the end f the period (in shares) at Sep. 30, 2020	25,402,000
Balance at the end of the period at Sep. 30, 2020	$ 243,852
Balance at the beginning of the period (in shares) at Dec. 31, 2019		2,290,000
Balance at the beginning of the period at Dec. 31, 2019	(143,837)	$ 0	4,808	4	(148,649)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(37,741)
Balance at the end of the period (in shares) at Sep. 30, 2020		4,620,000
Balance at the end of the period at Sep. 30, 2020	$ (168,431)	$ 0	17,951	7	(186,389)
Balance at the beginning of the period (in shares) at Mar. 31, 2020	21,073,000
Balance at the beginning of the period at Mar. 31, 2020	$ 173,447
Redeemable Convertible Preferred Stock
Issuance upon exercise of warrants (in shares)	45,000
Issuance upon exercise of warrants	$ 230
Balance at the end f the period (in shares) at Jun. 30, 2020	21,118,000
Balance at the end of the period at Jun. 30, 2020	$ 173,677
Balance at the beginning of the period (in shares) at Mar. 31, 2020		2,892,000
Balance at the beginning of the period at Mar. 31, 2020	(155,385)	$ 0	6,393	(3)	(161,775)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of vested options (in shares)		218,000
Issuance upon exercise of options	979		979
Stock-based compensation expense	445		445
Unrealized loss on cash equivalents	26			26
Net loss	(12,606)				(12,606)
Balance at the end of the period (in shares) at Jun. 30, 2020		3,110,000
Balance at the end of the period at Jun. 30, 2020	$ (166,541)	$ 0	7,817	23	(174,381)
Redeemable Convertible Preferred Stock
Issuance upon exercise of warrants (in shares)	531,000
Issuance upon exercise of warrants	$ 3,209
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)	5,227,000
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	$ 76,486
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)	(1,474,000)
Issuance of redeemable convertible preferred stock, net of issuance costs	$ (9,520)
Balance at the end f the period (in shares) at Sep. 30, 2020	25,402,000
Balance at the end of the period at Sep. 30, 2020	$ 243,852
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of vested options (in shares)		36,000
Issuance upon exercise of options	51		51
Stock-based compensation expense	563		563
Unrealized loss on cash equivalents	(16)			(16)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)		1,474,000
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	9,520		9,520
Net loss	(12,008)				(12,008)
Balance at the end of the period (in shares) at Sep. 30, 2020		4,620,000
Balance at the end of the period at Sep. 30, 2020	$ (168,431)	$ 0	17,951	7	(186,389)
Balance at the beginning of the period (in shares) at Dec. 31, 2020	25,402,402
Balance at the beginning of the period at Dec. 31, 2020	$ 243,854
Balance at the end f the period (in shares) at Mar. 31, 2021	25,402,000
Balance at the end of the period at Mar. 31, 2021	$ 243,854
Balance at the beginning of the period (in shares) at Dec. 31, 2020		4,713,000
Balance at the beginning of the period at Dec. 31, 2020	(182,894)	$ 0	18,788	(14)	(201,668)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of vested options (in shares)		504,000
Issuance upon exercise of options	1,225		1,225
Stock-based compensation expense	650		650
Unrealized loss on cash equivalents	(16)			(16)
Net loss	(12,822)				(12,822)
Balance at the end of the period (in shares) at Mar. 31, 2021		5,217,000
Balance at the end of the period at Mar. 31, 2021	$ (193,857)	$ 0	20,663	(30)	(214,490)
Balance at the beginning of the period (in shares) at Dec. 31, 2020	25,402,402
Balance at the beginning of the period at Dec. 31, 2020	$ 243,854
Balance at the end f the period (in shares) at Sep. 30, 2021	0
Balance at the end of the period at Sep. 30, 2021	$ 0
Balance at the beginning of the period (in shares) at Dec. 31, 2020		4,713,000
Balance at the beginning of the period at Dec. 31, 2020	(182,894)	$ 0	18,788	(14)	(201,668)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(41,505)
Balance at the end of the period (in shares) at Sep. 30, 2021		43,472,000
Balance at the end of the period at Sep. 30, 2021	$ 283,312	$ 0	526,526	(41)	(243,173)
Balance at the beginning of the period (in shares) at Mar. 31, 2021	25,402,000
Balance at the beginning of the period at Mar. 31, 2021	$ 243,854
Redeemable Convertible Preferred Stock
Issuance upon exercise of warrants (in shares)	4,448,000
Issuance upon exercise of warrants	$ 84,710
Balance at the end f the period (in shares) at Jun. 30, 2021	29,850,000
Balance at the end of the period at Jun. 30, 2021	$ 328,564
Balance at the beginning of the period (in shares) at Mar. 31, 2021		5,217,000
Balance at the beginning of the period at Mar. 31, 2021	(193,857)	$ 0	20,663	(30)	(214,490)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of vested options (in shares)		575,000
Issuance upon exercise of options	1,415		1,415
Stock-based compensation expense	725		725
Unrealized loss on cash equivalents	(9)			(9)
Net loss	(14,580)				(14,580)
Balance at the end of the period (in shares) at Jun. 30, 2021		5,792,000
Balance at the end of the period at Jun. 30, 2021	$ (206,306)	$ 0	22,803	(39)	(229,070)
Redeemable Convertible Preferred Stock
Issuance upon exercise of warrants (in shares)	62,000
Issuance upon exercise of warrants	$ 970
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)	(29,912,000)
Issuance of redeemable convertible preferred stock, net of issuance costs	$ (329,534)
Balance at the end f the period (in shares) at Sep. 30, 2021	0
Balance at the end of the period at Sep. 30, 2021	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of vested options (in shares)		229,000
Issuance upon exercise of options	855		855
Stock-based compensation expense	925		925
Unrealized loss on cash equivalents	(2)			(2)
Conversion of redeemable convertible preferred stock to common stock upon initial public offering (in shares)		29,912,000
Conversion of redeemable convertible preferred stock to common stock upon initial public offering	329,534		329,534
Issuance of common stock upon Initial public offering, net of issuance costs (in shares)		7,539,000
Issuance of common stock upon initial public offering, net of underwriting discounts, commissions and offering expenses of $16,076	172,409		172,409
Net loss	(14,103)				(14,103)
Balance at the end of the period (in shares) at Sep. 30, 2021		43,472,000
Balance at the end of the period at Sep. 30, 2021	$ 283,312	$ 0	$ 526,526	$ (41)	$ (243,173)