Theme (What is the game about?)
Players will control bodyguards and level them up to defeat the end level boss and save the princess
References
Castle Raid! - Apps on Google Play
Mechanics (What does the player do?)
Players control a level 1 bodyguard. By collecting bodyguards with the same level, they merge and upgrade to level 2. For example, if players have a level 1 bodyguard and collect another level 1 bodyguard, these two will merge and form a level 2 bodyguard.
Moreover, there are level-up gates in the game. After passing each level up gate, players receive a bodyguard with the same level as the gate. Players can choose between receiving a level 3 bodyguard or 3 level 1 bodyguards.
Goal is to upgrade bodyguards as much as you can and defeat the end level boss to save the princess
References
End level
DNA Evolution 3D - Apps on Google Play
Merging
Pusher 3D - Apps on Google Play
Gates
Count Masters: Crowd Clash & Stickman Running Game - Apps on Google Play
Describe 1 level (How do you win/lose? what is the challenge?)
- Players start by controlling a level 1 army man
- Players can move army man by swiping left and right
- Players can collect bodyguards with different levels
- Bodyguards with the same level will merge and level up
- Merging will reward players with currency
- After leveling up, attack and health will increase
- Players have choices on level up gates. Each gate will give bodyguards according to gate's UI
- Negative obstacles are enemies
- After fighting enemies, if the bodyguard's heath reduces to 0, it destroys
- After passing the finish line, players fight a boss in a castle who has captured the princess
- Army man level must be enough for defeating the boss
- Players must tap fast in the end level to defeat the boss faster
References

Twist (What makes the player go "woooow"?)
- Leveling up characters and watching them grow stronger and cooler
- Calculating which gate will end up with higher level bodyguards which makes players feel smart
- Defeating a higher level boss by rapidly tapping which makes players feel they played very well
References
Pusher 3D - Apps on Google Play
Pastebin (What Else is there?)