Download Discounts for Mar. 1: Sentinel: Mars Defense, Doodle Train, Particula

How about some free games to pick you up at the beginning of the month? We’ve got ‘em, in the form of two puzzlers and a tower defense game for the sci-fi-minded among us. Start with Sentinel: Mars Defense, in which your towers lay waste to aliens attempting to destroy your Martian base. After that, there’s Doodle Train, a game filled with train-based puzzles; and finally, Particula, one of our Games of the Week picks, goes free.

Sentinel: Mars Defense (iPhone) Free (was $0.99)

Sci-fi tower defense: That’s what’s on offer in Sentinel: Mars Defense, in which you’ll fight off hordes of aliens on several different levels composed of Martian trenches. Each level goes on for quite a while — the first one features 60 waves of enemies — and includes two different game modes to keep you challenged and engaged.

Sentinel adds more levels to the strategy inherent in tower defense by allowing you to rely on barriers and requiring attention to be paid to landscape layout for maximum effectiveness. It packs some quality graphics, and it automatically saves your progress if you’re interrupted, to make sure you won’t lose your long-haul progress.

Doodle Train (iPhone) Free (was $0.99)

A track-based puzzler with crayon graphics and lots of content, Doodle Train gives you a puzzle and requires you to figure out how to complete tracks and help a train reach its destination. Tapping on different elements like switch tracks lets you alter the path, and you’ll need to think creatively and logically to figure out how to make it through puzzles as quickly as possible.

The game includes more than 100 levels and tracks your progress on global leaderboards from Scoreloop. It also contains four game modes: “Labyrinth,” a puzzle mode; “Build Railroad,” which is more action-based; “Snake,” another action-packed mode; and “Longest Railroad,” which mixes action with puzzle elements.

Particula (iPhone) Free (was $0.99)

Puzzler Particula just came out last week, and it’s already available for free for a limited time, so grab it while you can. It requires you to use physics to help charged particles pass electrons to one another. That’s a scientific description for a game that’s intuitive but definitely challenging, with the electrons you try to shoot around the level being effected by magnets and polarity along the way.

Particula includes Game Center support for leaderboards and achievements, and each puzzle includes three stars you must figure out how to grab to earn the highest available score. The tricky parts come in puzzles in which you’re required to move magnets around and determine their effect based on their polarity.

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