Comparison

Idle Defender vs Kessler Sky

Price, ratings, monetisation and update history for both games, side by side — with what reviewers say about each.

Head to head
About

Idle Defender

Engage in an addictive incremental tower defense experience. Strategically build and upgrade towers to fend off monster raids, expand your territory, and generate idle income. Collect ability cards and research upgrades to become an invincible defender.

Highlights
  • Auto idle tower defense
  • Build and upgrade towers
  • Simulate monster battles
  • Upgrade special abilities
  • Discover chests and mines
  • Collect ability cards
  • Generate idle income offline
Features
Read full description

Idle Defender is an addicting incremental game in the tower defense genre with elements of expansion and idle games. Defend the tower zone, which is automatically attacked by monster raids. Combine idle strategy and automatic battles to protect your territories and stop the conquer and tower smash. Build and upgrade a strong tower, defend your territory, and become a champion on the battlefield! Fight off waves of enemies, defend your base, and expand your tower's control radius this idler. Capture mines and chests to earn money, crystals, and ability cards! Reach new levels and unlock new features. Become more powerful and stop the tower conquerors. Join us and become the best idle tower defender! KEY FEATURES - Auto idle tower defense for all players! - Build and upgrade tiny towers to expand your territory and gain more resources! - Simulate battles between a tower and hordes of monsters! - Upgrade special abilities, grow defense, and reduce damage from attacks! - Discover various chests and mines around the towers for additional resources! - Collect cards that add capabilities to towers! - Constantly improve attack and defensive systems against monsters! - Research new upgrades to unlock more parts of the idle game! - Generate idle income in tower defense offline! - Enjoy the addicting incremental gameplay! If you fun of base defense games or idle simulation games, don’t wait! Idle Defender is the ultimate tower defense game for idle game enthusiasts with ever-evolving strategies! Playing this idle defense game is easy. Strategically manage tense and exciting battles. Prevent monsters from destroying the core defense and surrounding areas. Unlock powerful upgrades and abilities to build an even stronger tower. Upgrade your skills, command the battlefield, and become invincible! We’re always happy to hear from our players! Email us your ideas: support@crootosoftware.com NOTE: Idle Defender: Tower Defense is free idle game, but some game elements can be purchased with real money. You can disable in-app purchases in your device settings. A secure internet connection is required to play this incremental idle game.

About

Kessler Sky

Manage Earth's launch pad by strategically launching satellites. Dock them to build larger structures and earn income, but avoid collisions that create debris and lead to system failure. Compete with friends and complete daily contracts to keep the sky open.

Highlights
  • One-thumb satellite launching
  • Satellite docking for larger structures
  • Debris collision system
  • Daily contracts and leaderboards
  • Offline play
  • Optional ad rewards
Features
Read full description

You run Earth's launch pad. Hold to choose an altitude, let go to launch. Satellites that meet in the same orbit dock into bigger ones: cubesat, comsat, telescope, lab, station, ring habitat, Gateway. Every lap they fly pays you. Cross two orbits and they collide. The debris keeps orbiting and shreds whatever it meets next. When the debris wins, the sky closes. That is the Kessler syndrome. It is your fault. You will want to go again. ONE THUMB - Hold anywhere: the marker climbs the orbit shells. Let go: launch. - Release with the arrow straight for a clean circle; release off-centre for an ellipse that crosses traffic. - The path preview turns red when it will cross an occupied shell. Every crash is a choice you made. BUILD THE SKY - Same shell, same kind: they dock into the next tier. Seven tiers, from a cubesat to the Gateway. - Build a Gateway and the Moon comes online: double income for the rest of the run. - Three daily contracts give every run a purpose beyond the score. DAILY SKY - The same satellite queue for everyone, once a day. One attempt counts, practice is unlimited. - Share your sky as a spoiler-free card. Beat your friends on the leaderboard. HONEST AND LIGHT - Plays offline. Progress saves on your device. - Free. Optional ads only: watch one to send the Sweeper drone or double your coins. - No account, no login, no permissions beyond the basics. Hand-drawn pixel art, original music and sound. Built by a small studio that wanted a space game you can understand in one second and play for a month. How long can you keep the sky open?

Screenshots

Idle Defender4 screens
Kessler Sky4 screens

Verdict

The call

The clearest difference is in-app purchases: Kessler Sky at none against Idle Defender's 2. Kessler Sky also leads on rating (5.0 vs 4.5). Idle Defender's advantage is ads (none vs shown) and ratings volume (11 vs 1). On price, update cadence, monetization model and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Idle Defender sells 2 one-off in-app purchases. Kessler Sky asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Kessler Sky holds the better App Store score, 5.0 against 4.5. That said, the two scores are not equally well evidenced: Idle Defender has 11 ratings behind it against 1, so its average is the more settled of the two.

UpkeepUpdate frequency

Idle Defender ships an update every 2 months, Kessler Sky monthly. The most recent releases landed on October 24, 2026 and October 23, 2026 respectively.

Scorecard4 real differences · 6 level
Idle Defender versus Kessler Sky: the parameters behind the verdict, then further details
ParameterIdle DefenderKessler Sky
PriceFreeFree
Rating4.5 (11 ratings)5.0 (1 ratings) — better
Positive reviews75.0% of reviews—
Number of ratings11 — better1
Update frequencyEvery 2 monthsMonthly — better
AdsNo — betterYes
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree with in-app purchases
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS15.015.0
Further details — not scored
Size181 MB6 MB
Age rating4+4+
DeveloperCROOTOTHE RISE COLLECTION

Customer experience

Idle Defender

All ratings11 ratings
Positive90.9%
Neutral0.0%
Negative9.1%
Written reviews4 reviews
Positive75.0%
Neutral0.0%
Negative25.0%

Kessler Sky

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

2 purchases

Idle Defender

One-time2
  • Buy No Ads$5.99
  • Buy No Ads Full$17.99
None

Kessler Sky

No in-app purchases

Questions

Is Idle Defender free?
Idle Defender is free to download, with in-app purchases available.
Is Kessler Sky free?
Kessler Sky is free to download, with no in-app purchases.
Which has better reviews, Idle Defender or Kessler Sky?
Kessler Sky is rated higher. Idle Defender averages 4.5 out of 5 from 11 ratings, while Kessler Sky averages 5.0 from 1 ratings.
Do Idle Defender or Kessler Sky have ads?
Kessler Sky shows ads; Idle Defender does not.
Which is updated more often, Idle Defender or Kessler Sky?
Idle Defender ships an update every 2 months, and Kessler Sky monthly. Most recently, Idle Defender was updated on October 24, 2026 and Kessler Sky on October 23, 2026.

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