Treat your brain to some crazy 3-D puzzle action in Pangea’s Enigmo 2. We also have an educational app that will help your child increase their vocabulary, and an effects app that will breath new life into your outdoor photos.

All app prices are subject to change at any time and without notice regardless of stated free duration. Price changes are solely under the control of the developers.

iPhone:

PreCalculus Pro ($0.99 → Free, 1.6 MB): This education app offers a rich collection of precalculus solvers, tutorials, and examples for a wide range of topics. You’re able to scroll through the large list of topics or you can search for something specific. Topics include inverse functions, logarithms, conic sections, limits, polar curves, compound interest, and much more.

PreCalculus Pro is available for free for a limited time. It has a 4-star rating with a total of 12 ratings.

War of the Fallen ($9.99 → Free, 45.9 MB): ★★★★★ TODAY ONLY DEAL ★★★★★ Get 90 Gems, 5 Stamina Elixirs, 3 Attack Mana Potions, and a Magic Shield for free! That’s a $10 Value!★★★★★★★★★★★★★★★★★★★

Join the Cult of the Darkstar, Iron Legion, or The Corrupted and fight your way to the top in this card combat game. You should probably join the Iron Legion because the good guys always win. But hey, whatever you want. It’s your deck. Take on quests and battle against powerful opponents to collect new cards and level them up. Then join a guild and build up your guild force to conquer other players around the world. The game includes gorgeous animated cards, offensive and defensive decks, and more than 100 special battle skills.

War of the Fallen is available for free for a limited time. It has a 4.5-star rating with a total of 109 ratings.

HDR FX Pro ($1.99 → Free, 23.3 MB): Trying to take outdoor photos with your iPhone or iPod touch can be an awful, terrible experience. But it doesn’t have to be! HDR FX Pro is able to mask any deficiencies in your outdoor photos by applying HDR effects. The 42 HDR presets are broken down into three categories: scenery, sky, and ground. You’re able to view a preview of each one and see which come highly recommended. After settling on an effect, you can further customize your photo with textures, borders, and the app’s other powerful editing tools.

HDR FX Pro is available for free today only (04/25). It has a 4-star rating with a total of 100 ratings.

Universal:

Otto Matic ($2.99 → Free, 65.2 MB): Otto Matic is the only one that stands in the way of the evil Brain Aliens who are out to abduct and enslave every last human. Help him save all of humankind in this 3-D adventure game. You’re able to make your way through the 10 different worlds using on-screen controls. Battle aliens, ride bumper cars, pilot saucers, ride zip lines, and do whatever else it takes to defeat the scum of the universe. The game also includes 25 alien creatures, and seven weapon types.

Otto Matic is available for free today only (04/25). It has a 3.5-star rating with a total of 801 ratings.

Billy Frontier ($2.99 → Free, 32.2 MB): Billy Frontier isn’t just a regular old cowboy. He’s a space cowboy on a mission to rid the galaxy of alien outlaws! Help him earn his badge by firing at anything that moves and outrunning stampedes in this collection of mini-games. It includes a total of eight missions to conquer, all of which also feature their own local leaderboards.

Billy Frontier is available for free today only (04/25). It has a 3-star rating with a total of 5466 ratings.

Bugdom 2 ($2.99 → Free, 63.0 MB): Play as Skip McFly, a grasshopper on a journey to discover new areas inside and around a house, in this 3-D adventure game. On-screen controls allow you to run around the open environments, jump over obstacles, and stomp out enemies. The game also includes AirPlay support, so you can play on a much bigger screen.

Bugdom 2 is available for free today only (04/25). It has a 3-star rating with a total of 5705 ratings.

Nanosaur 2 ($3.99 → Free, 50.7 MB): Pilot a pterodactyl equipped with massive firepower through dangerous environments to retrieve the missing eggs in this 3-D adventure game. Trust me, this pterodactyl is much, much cooler than a shark with laser beams attached to its head. Just tilt to steer and tap to fire your massive weapons. Collect power-ups to gain new weapons and wipe out entire defense systems. The game includes four modes, online multiplayer, and achievements and leaderboards via Game Center.

Nanosaur 2 is available for free today only (04/25). It has a 3.5-star rating with a total of 6585 ratings.

Cro-Mag Rally ($3.99 → Free, 86.9 MB): Play as Brog the caveman and speed through the Stone, Bronze, and Iron Ages in this 3-D racing game. You’re able to steer your vehicle using tilt controls, and tap to fire your weapons and activate your power-ups. The game includes nine tracks, 11 vehicles, nine power-ups, and multiplayer via Game Center.

Cro-Mag Rally is available for free today only (04/25). It has a 3.5-star rating with a total of 20162 ratings.

Space Twinkle ($0.99 → Free, 63.3 MB): Make Space Twinkle with your fingers with this generative art app. Place anywhere from a single finger to all 10 of them on the screen and watch what happens. Each additional finger will cause the particles on the screen to act in a different way, so make sure to experiment with them. You can tap any corner of your screen to bring up the option to snap a photo or change the particle settings.

Space Twinkle is available for free today only (04/25). It has a 5-star rating with a total of 31 ratings.

Enigmo 2 ($2.99 → Free, 14.7 MB): A total treat for your brain. Engimo 2 requires you to manipulate streams of falling water, plasma, and laser beams in order to get them into their appropriate containers. You have all kinds of tools at your disposal, which can be twisted and turned within the 3-D environments. The game includes 50 levels, and achievements and leaderboards via Game Center.

Enigmo 2 is available for free for a limited time. It has a 3.5-star rating with a total of 2669 ratings.

Ride a Pony with Kate and Harry ($1.99 → Free, 36.3 MB): Your little one can let their imagination run wild by designing and dressing up ponies to ride. They first get to pick Kate or Harry to be their helper. They can then dress up their own pony just by tapping on different items. When they’re ready, they can have Kate or Harry ride the pony through randomly generated and interactive environments.

Ride a Pony with Kate and Harry is available for free today only (04/25). It has a 4.5-star rating with a total of 8 ratings.

Hidden Doodles ($0.99 → Free, 102.8 MB): A beautifully crafted hidden objects game that will challenge your memory and your patience. The main Mission mode presents you with multiple doodles to find. Try to memorize them, because you won’t see them again until you find them within the visual puzzle. Your score is based on how fast and how efficient you are at finding the doodles. The game includes 100 puzzles, an arcade mode, a two-player mode, iCloud support, and achievements and leaderboards via Game Center.

Hidden Doodles is available for free for a limited time. It has a 4.5-star rating with a total of 52 ratings.

iPad:

iLuv Drawing Dinosaurs HD – Learn how to draw dinosaurs step by step ($2.99 → Free, 44.9 MB): Learn how to draw adorable dinosaurs with this fun education app. It guides you through each step of the process with lines to trace and audio instructions. You’re able to choose from a variety of pen colors and sizes, custom background textures, and stickers. It also includes undo and redo, an eraser, a blank page for doodling, and the ability to save your final project.

iLuv Drawing Dinosaurs HD – Learn how to draw dinosaurs step by step is available for free for a limited time. It has a 4-star rating with a total of 32 ratings.

Sight Words & Spelling with Pixopop HD ($2.99 → Free, 19.2 MB): This educational app will help your child increase their vocabulary in a fun new way. They get to join Stitch Bunny and his friends as they learn 240 common sight words through interactive flash cards. Each word can be tapped on to be sounded out. Your child can then take the word and spelling challenges to see how much information they have retained. The app also includes customizable words lists, stat tracking, and trophies to earn.

Sight Words & Spelling with Pixopop HD is available for free for a limited time. It has a 4.5-star rating with a total of 23 ratings.

That concludes today’s issue of Apps Gone Free. If you like staying on top of these daily deals, don’t forget to check out our free AppsGoneFree app. It provides all the deals each day, and even an archive of past deals that are still active.

Developers:

If you are a developer who would like to get your app included in our “Apps Gone Free” daily lists, here’s our basic set of rules:

  • It must have at least a three-star average rating at the time it goes free.
  • The app must not have been free numerous times (3+) over the last six months.
  • The free version of your app must not include ads.

To submit an app, simply send a request to tyler@appadvice.com with the subject “Apps Gone Free.” Please include the name of the app, a link to it in the App Store, when and for how long you intend to offer the app for free, and anything else you would like to share. We will take it from there.