TL;DR: awesome game. Extremely fun to play. Completely worth its full price.

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Supraland is such a great game. Haven't had this much fun playing a game in years.

Normally, I go the r/patientgamers route and wait until a game has a discount of at least 50% before buying it. I've too many games on my backlog anyway.
Not Supraland, though. From the moment I first watched the trailer, I knew I was gonna love it.
I was lucky enough to get a relatively low discount – like 15% or 20% –, but, TBH, I'd have bought it regardless. I haven't regretted a single cent I spent.

The first reason why it's so great is the "awe factor".
It's marvelously set entirely within a child's sandbox. All elements, including characters, items and scenery, are created from household items, much like a child playing would do. In fact, much like I used to do when I was little.
This somewhat simple, yet inspiredly innovative æsthetic choice creates a difficult-to-describe-yet-obvious-once-experienced nice feeling: a perfect balance between affectionate familiarity and adventurous excitement.
I. E.: it captures the essence of childhood.

The only other games I've played that get close to this are the acclaimed LEGO series . And, to me, they still fall short of what Supraland achieves.

The second reason why Supraland's so great, however, is kinda subtler:

The game features a "barebones" gameplay that is very uncommon these days.
I like complex games, but too many games these days are unnecessarily complex: mechanics for the sake of mechanics.

People constantly bash microtransactions and loot boxes and, yes, those surely are awful. But there are lots of games that have no microtransaction, loot boxes or any other "greedy" mechanic at all and still feature unneeded complexity that detracts from the experience.
As the industry evolved, titles were expected to include more and more features, often leading to oversaturation.
The best example of this I can cite is Darksiders II . It isn't a bad game, but it was – IMO – made orders of magnitude inferior to its predecessor due to the completely unnecessary introduction of MMORPG-style loot mechanics.

Supraland, in its simple glory, evokes pre-BotW Zelda games, the Portal series and other celebrated games that are just fun, without trying too hard.

I believe I haven't been this enamored of a game since I first played Terraria .

P.S.: I think the game deserves an honorary mention for the fact that David Münnich, the developer, made this great a game all by himself.
It'd have been no mean feat for a big company to make a game like this. But a single person? Almost unbelievable.