I don’t really want to spoil too much, but try to invest the coins you get into powerups and try going for relics in the stages (follow green arrow in stages with !). The unlocks screen also has good pointers for what to do next.
Don’t worry about dying quickly if you’re only just started, it’s all part of the game.
It won’t kill the full 20 hours, but 2 great mobile games that I like without the gambling bullshit: Vampire Survivors and Siralim Ultimate. The first one is free, so just try it. The second one is a monster training RPG where you can make sick combos and synergies.
One of my favourite games. Great choice if you like puzzles!
Hate to burst your bubble, but the calcium inside your bones is not in a metallic form but as calciumphosphate. So no metal frame but one made of a salt I guess.