In Dungeon Raid, you start off a new game by selecting a difficulty level (Easy, Normal, Hard or Harder) and an adventurer class. At the start of the game, you only have one choice, the Adventurer, with no options for customizing any part of it. As you play the game, more classes will be unlocked, along with customization options for them in the forms of different perks and difficulties that will be applied. The classes do end up playing differently, especially when you start dealing with the nemesis of each class, and having unlockables to strive for is always nice. After you have your character selected, it's off into the dungeon.
The main screen includes a 6 by 6 array of icons, which typically are swords, shields, potions, coins or skulls. You trace a path with your finger to connect three or more of the same symbol, including diagonally. What happens next depends on the icons you traced. For shields, you increase your stored defense with the excess going towards equipment upgrades. Coins increase your treasury, which will eventually give you more equipment to purchase. Potions will heal your character. Finally, swords and skulls are matched, with the latter being monsters with attack, defense and health values. You generate damage to monsters when you connect swords to them, using your character's base damage with a bonus for each sword connected in a run. Subtract the target's defense and apply the result to its health. When you blow up a skull, you get experience to allow your character to level up (and gain benefits). After you trace, the icons disappear and stuff falls down from the top.
On top of this basic chassis, your character will earn skills which have a variety of effects (many of them pretty significantly changing the game state) and there are also boss monsters who show up. Those boss monsters take some planning to deal with, especially a nemesis monster, who will have special requirements for what you have to do to defeat them. Things can go south in a hurry if you aren't careful. It's also the case that the decisions you make on what to upgrade, what stuff to purchase and what upgrades to get upon leveling up is non-trivial, and you have to decide on a strategic approach to the game. Those upgrades also come at a good pace, keeping you interested, and the boss monsters show up at a good pace as well.
There are also a lot of very professional things to appreciate about the game. It does a great job of saving your state all the time, so you can hop in and resume a game quickly right where you left off, a feature that is really important to me. There is a well-done tutorial to get you running quickly. There is a great variety of equipment, skills, monsters and character classes to keep you interested, meaning that despite the relative simplicity of the basic game, there is a lot going on. I also like that the game can get vicious in a hurry. The developer has done a great job tuning the game to be quite engaging. The physical mechanics of playing the game are also pleasant, with the act of tracing a really long path being quite satisfying. While it shares the attributes of casual games in how quickly you can pick it up, I think there's some good depth here, and it's quickly become a favorite on my phone. I'm going to give it 4.5 stars out of 5.