Rivets and Rebellion

Overview

Rivets and Rebellion is a solo-developed 2D platformer shooter set in a near-future city where factory robots have gone rogue. Players take the role of a lone officer armed with a six-shot revolver, navigating an eight-section factory level through running, crouching, climbing, jumping, and dashing, culminating in a multi-phase boss fight against Mega V. Inspired by Metroidvania titles like Hollow Knight, the game emphasizes precise movement, tactical combat, and environmental awareness. I handled all aspects of design, programming, level design, and character animation.

Problems Addressed

• Metroidvania skill progression in level design: Six levels each introduce a distinct mechanic — aerial enemy evasion, flanking shielded robots, moving platform combat, and charged shots for armor — building competence progressively.
• Revolver resource management tension: A six-shot capacity with manual reload forces players to manage ammunition within combat rhythm, creating pressure during critical encounters.
• Multi-phase boss synthesizing all skills: Mega V's three phases (parabolic bullet patterns, summoning reinforcements with increased attack speed, periodic shield phase) require players to integrate every skill learned throughout the game.
• Spine 2D skeletal animation visual consistency: Character animations needed smooth transitions across states (Idle, Dashing, hit, death) while staying coherent with the game's silhouette-based visual style.

Solution & Implementation

• Eight-section continuous level structure: Designed a single large level divided into eight sections, with a flowchart mapping each section's mechanic focus to ensure players master each skill before facing the next challenge.
• Boosted bullet system: Implemented charged shot logic allowing boosted bullets to break armored doors and boss shields, introduced in Level 5 and reused as a critical mechanic in the final boss encounter.
• Mega V three-phase state machine: Implemented HP threshold-based phase transitions — Phase Two triggers reinforcement spawning and attack acceleration at half health; Shield Phase periodically enables invincibility requiring boosted bullets to break.
• Spine skeletal animation integration: Used Spine to create skeletal animations for the player and enemies (Spider, Drone, Tank), integrated into Unity2D with an animation state machine managing transitions, ensuring fluid movement and consistent visual style.
• Iterative level design: Conducted playtests and collected feedback, adjusting level parameters based on player responses to difficulty spikes and low error tolerance in later stages to improve overall playability.

Tech Stack

• 引擎 / Engine：Unity2D
• 语言 / Language：C#
• 动画 / Animation：Spine（2D 骨骼动画）
• 关卡构建 / Level：Unity Tilemap

Key Features

• Eight-section level with six progressively introduced mechanics
• Six-shot revolver with manual reload and charged boosted bullets
• Three-phase boss Mega V (parabolic bullets, reinforcement summons, shield phase)
• Three enemy types: Spider (melee), Drone (aerial), Tank (shielded)
• Invincibility-frame dash through enemies and bullets
• Spine skeletal animation covering all player and enemy states
• Heart HP UI + bullet count and skill bar HUD

Challenges & Tradeoffs

• First Metroidvania level design attempt: As a first attempt at this genre's level design, some sections had room for improvement in exploration guidance and spatial layout — playtests flagged steep difficulty spikes in later levels.
• Limited replayability: After completing the full run and defeating the boss, there is limited motivation to replay. Scoring or randomization mechanics were not implemented in the initial version.
• Spine animation parameter tuning: Matching animation sets to the game's visual style required extensive research and external feedback, consuming significant iteration time.

Results & Impact

The game delivered a complete playable build with six levels and a three-phase boss encounter. Playtesting collected and integrated player feedback, receiving positive responses for intuitive combat systems and gradual mechanic introduction, while identifying the difficulty curve and replayability as areas for future improvement.

Next Steps

• Adjust late-game difficulty curve and error tolerance to reduce frustration for new players.
• Introduce new enemy types to increase combat variety and strategic depth across levels.
• Explore a scoring system or randomization elements to improve long-term replayability.