Condensed Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	IPO	Public Offering	Common Stock	Common Stock IPO	Common Stock Public Offering	Additional Paid-in Capital	Additional Paid-in Capital IPO	Additional Paid-in Capital Public Offering	Accumulated Other Comprehensive Loss	Accumulated Deficit	Convertible Preferred Stock
Balance at Dec. 31, 2019	$ (65,357)						$ (43,172)				$ (22,185)
Temporary equity, balance, Shares at Dec. 31, 2019												37,267
Temporary equity, balance at Dec. 31, 2019												$ 134,720
Balance, Shares at Dec. 31, 2019				2,989
Issuance of common stock upon exercise of stock options, net of repurchases	16						16
Issuance of common stock upon exercise of stock options, net of repurchases, Shares				41
Vesting of early exercise options	14						14
Issuance of convertible preferred stock, net of issuance costs												$ 2,200
Issuance of convertible preferred stock, net of issuance costs, Shares												538
Stock-based compensation	449						449
Net loss	(6,085)										(6,085)
Balance at Mar. 31, 2020	(70,963)						(42,693)				(28,270)
Temporary equity, balance, Shares at Mar. 31, 2020												37,805
Temporary equity, balance at Mar. 31, 2020												$ 136,920
Balance, Shares at Mar. 31, 2020				3,030
Balance at Dec. 31, 2019	(65,357)						(43,172)				(22,185)
Temporary equity, balance, Shares at Dec. 31, 2019												37,267
Temporary equity, balance at Dec. 31, 2019												$ 134,720
Balance, Shares at Dec. 31, 2019				2,989
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	120
Net loss	(28,080)
Balance at Sep. 30, 2020	320,164			$ 4			370,425				(50,265)
Balance, Shares at Sep. 30, 2020				37,527
Balance at Mar. 31, 2020	(70,963)						(42,693)				(28,270)
Temporary equity, balance, Shares at Mar. 31, 2020												37,805
Temporary equity, balance at Mar. 31, 2020												$ 136,920
Balance, Shares at Mar. 31, 2020				3,030
Vesting of early exercise options	34						34
Issuance of stock, net of issuance costs, Value		$ 274,054			$ 2			$ 274,052
Issuance of stock, net of issuance costs, Shares					16,560
Conversion of convertible preferred stock into common stock upon completion of initial public offering	136,920			$ 2			136,918					$ (136,920)
Conversion of convertible preferred stock into common stock upon completion of initial public offering, Shares				17,921								(37,805)
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	120						120
Cashless exercise of common stock warrants, Shares				16
Stock-based compensation	687						687
Net loss	(10,556)										(10,556)
Balance at Jun. 30, 2020	330,296			$ 4			369,118				(38,826)
Balance, Shares at Jun. 30, 2020				37,527
Vesting of early exercise options	11						11
Stock-based compensation	1,296						1,296
Net loss	(11,439)										(11,439)
Balance at Sep. 30, 2020	320,164			$ 4			370,425				(50,265)
Balance, Shares at Sep. 30, 2020				37,527
Balance at Dec. 31, 2020	306,223			$ 4			372,764			$ (5)	(66,540)
Balance, Shares at Dec. 31, 2020				37,569
Issuance of common stock upon exercise of stock options	24						24
Issuance of common stock upon exercise of stock options, Shares				31
Vesting of early exercise options	10						10
Stock-based compensation	3,701						3,701
Net loss	(23,844)										(23,844)
Other comprehensive gain (loss)	2									2
Balance at Mar. 31, 2021	286,116			$ 4			376,499			(3)	(90,384)
Balance, Shares at Mar. 31, 2021				37,600
Balance at Dec. 31, 2020	$ 306,223			$ 4			372,764			(5)	(66,540)
Balance, Shares at Dec. 31, 2020				37,569
Issuance of common stock upon exercise of stock options, Shares	114
Reclassification of warrant liability to equity due to adjustment from preferred stock warrant to common stock warrant upon completion of initial public offering	$ 0
Net loss	(79,471)
Balance at Sep. 30, 2021	394,877			$ 5			540,884			(1)	(146,011)
Balance, Shares at Sep. 30, 2021				46,897
Balance at Mar. 31, 2021	286,116			$ 4			376,499			(3)	(90,384)
Balance, Shares at Mar. 31, 2021				37,600
Issuance of common stock upon exercise of stock options	98						98
Issuance of common stock upon exercise of stock options, Shares				51
Issuance of common stock under employee stock purchase plan	318			$ 14			318
Vesting of early exercise options	9						9
Stock-based compensation	4,289						4,289
Net loss	(26,353)										(26,353)
Other comprehensive gain (loss)	3									3
Balance at Jun. 30, 2021	264,480			$ 4			381,213				(116,737)
Balance, Shares at Jun. 30, 2021				37,665
Issuance of common stock upon exercise of stock options	34						34
Issuance of common stock upon exercise of stock options, Shares				32
Vesting of early exercise options	6						6
Issuance of stock, net of issuance costs, Value			$ 155,082			$ 1			$ 155,081
Issuance of stock, net of issuance costs, Shares						9,200
Stock-based compensation	4,550						4,550
Net loss	(29,274)										(29,274)
Other comprehensive gain (loss)	(1)									(1)
Balance at Sep. 30, 2021	$ 394,877			$ 5			$ 540,884			$ (1)	$ (146,011)
Balance, Shares at Sep. 30, 2021				46,897