Lucid is a match-something puzzle game. Like many of its kind, due to the nature of it, I won't recommend playing this on a PC. There's a reason why games like this found a better home on mobile and tablet devices, they're made for bitsize playthroughs to relax with simple controls in mind. Having said that, Lucid is not relaxing nor bitsize, it's more mind numbing and frustrating than anything else.
The game itself is fine for what it is, that is to say it's nothing special. You play through a series of levels with increasing difficulty. Each level starts on a preset board and requires you to clear more and more cubes. To clear cubes you need to draw a path across same-coloured blocks, you cannot clear a set if the path doesn't go across every adjacent same-colored block; this is where the frustration lies.
If a random block drops, breaking your built up combo, you'll just need to hope you get the right randoms to fix it while having other sets to clear bearing in mind that broken combo you built is still there taking up a lot of the board. So the randomness and clearing requirements work completely against each other and make it difficult to plan anything out without risking the entire game.
With nothing else to do but draw paths along blocks, the game eventually becomes repetitive and, other than achievements, there's not much insentive to keep going unless if you like more of the same. There's also no online nor offline leaderboards which is damaging for a game with a point system and a few hours worth of levels.
The music and graphics are also somewhat nauseating at first because of all the effects, especially how everything is bouncy and glowy. This is likely intentional going by the name of the game and you grow used to over time but it's still worth mentioning.
Finally, to nitpick, the menu (just one) in general is a bit weird. For example, there's a large "Delete Save" button which is placed directly under the "Start" button with no confirmation dialogue. So one misclick and your entire save will disappear. Another option is to "Sign In" which gave me hope for cross-device save syncing, a major convenience in this day and age, but it's just a save selector; not surprising since this game is so old. There's also "Options" which just lets you adjust sound volume, display resolution is limited and picked everytime you launch the game.
So to summarise, Lucid is a simple game with mechanics that work against each other to provide a not so relaxing experience.