Here is the full list of all 32 Inline achievements.
Repeatedly press ESC at the main menu to display the game with inversed colors
Reach combo of 3
Reach level 5
50 shapes placed
20 skips used
50 lines cleared in one session
Skip when no more skips are left
Lose with no lines cleared
Click and hold main menu title for 5 seconds
Spin one shape 20 times
Skip a single block
Drop a shape outside of the grid
Reach max level 10
Lose after using 5 skips in a row
Play Custom Mode
Beat your own highscore 3 times
Reach streak of 3
Play 20 normal games
Completed 3 lines in 9 moves
1000 lines cleared
Reached more than 9000 score in total
Reach streak of 5
Reach 600 score in 50 moves
Reach level 5 without skips
Reach a combo of 4
Find every easter egg
Rotate a shape that will not change the orientation
Type RAIN at the main menu and let the rain work its magic
Use the Gameboy command in the console and enjoy tastelessly emulated graphics from the past
Try to access debug features and meet their guardian
Push an AI to crash the game
Find the option hidden in the options menu, and enjoy them "soft-body physics"