Per Atari v. Philips, Tetris Holding v. Xio Interactive, and Spry Fox v. Lolapps, among other cases, substantial similarity in presentation is enough for a video game to infringe on another game's copyright, even if it shares no code or assets with the infringed-upon game. And yes, this means the idea that game mechanics or even "look and feel" are not copyrightable is a myth.
The concept of Tetris, in particular, is protected with copyright, patent, and trademark armor so thick that if you write a clone of the game, Henk and Alexey will sue you into a smouldering crater.
debian and ubuntu ship an implementation of tetris in the bsdgames package (and bsd has included it since the 80s), gnu emacs has included tetris.el for 25 years (despite removing yow lines), and debian also includes bastet, blocks of the undead, crack-attack, gtkboard, kblocks (which is part of kde), ltris, netris, petris, stax, termtris, tetrinet, tint, vdr-plugin-games, vitetris, /usr/share/vim-scripts/plugin/tetris.vim, and quadrapassel (which is part of the official gnome release)
you've been able to buy cheap '9999 in 1 block game' hardware with 200 nematic pixels, preprogrammed with tetris, for at least 15 years at any import port in the world
also, minecraft is just an infiniminer clone, and there are fifty zillion clones of each of pacman, space invaders, breakout, snake, doom, and super mario
so these novel legal precedents you mention, though indeed menacing, are at least still being very narrowly applied in practice; conflicting precedents include data east v. epyx, capcom v. data east, and atari v. amusement world
even in tetris v. xio, the judge held that tetris's gameplay is not copyrightable, and the case was not appealed, so it isn't binding precedent outside that one district
also your mention of patent suggests that maybe you're not very well informed about the area; tetris came out in 01985, so any patents on inventions disclosed by the game would have had to have an application date no later than 01986 (01985 outside the usa) and, barring lemelson-style submarine patent tricks to delay issuance until 02006 or later, be expired for over a decade now
>The patent protects the "Nemesis characters, nemesis forts, social vendettas and followers in computer games."
>This encompasses a hierarchy of procedurally-generated NPCs that interact with and remember the player's actions. The patent also covers changes to the NPCs' positions in the hierarchy, as well as their appearance and behaviour, again based on the actions of the player.
https://en.m.wikipedia.org/wiki/Idea%E2%80%93expression_dist...
Game mechanics pretty much can't be copyrighted at all.