> ## Documentation Index > Fetch the complete documentation index at: https://docs.summerengine.com/llms.txt > Use this file to discover all available pages before exploring further. # 2D Survivors - Progression (Make game skill) > 2d-survivors-progression.md from the Make game skill in the Summer Engine skill library. Orchestrate 'make me a game': brainstorm, plan, scaffold, mechanics, art, audio, polish, verify, ship. Part of the [`make-game` skill](/skills/make-game). The skill links here when your agent needs the detail. The systems layer on top of `2d-survivors.md`: enemy roster, wave-driven spawning, elites, level-up upgrades, the between-wave shop, weapon evolution, and characters. Build these only after the core loop (move + auto-fire + chase) runs. ## Enemy roster (one script, many behaviors) All types share `enemy_base.gd` (Area2D, "enemies" group), configured through `setup(type, wave)` - no per-type scenes. HP/speed scale with wave number: | Type | Behavior | Health | Speed | Special | | - | - | - | - | - | | Walker | chase + wobble | 15 + wave\*8 | 55 + wave\*2 | standard horde unit | | Runner | fast chase | 8 + wave\*4 | 110 + wave\*3 | 0.7x scale | | Tank | slow, big | 50 + wave\*15 | 35 + wave\*1 | 1.5x scale, 3 XP | | Boss | massive | 500 + wave\*80 | 45 | 2.8x scale, 25 XP | | Ranged | keeps distance | 12 + wave\*5 | 50 + wave\*1.5 | fires projectiles | | Charger | telegraph + dash | 20 + wave\*7 | 50 + wave\*1.5 | 550px/s burst | | Spawner | stays back | 80 + wave\*20 | 30 | spawns 2-3 minions | Behavior dispatch is a `match behavior:` in `_physics_process`. Give every enemy a randomized wobble (`_wobble_phase = randf() * TAU`, per-enemy speed and amplitude) so hordes look organic instead of converging in a straight line. Charger is a 4-state machine: WALK -> TELEGRAPH (0.45s, within 320px trigger range) -> CHARGE (0.4s at 550px/s in the locked direction) -> RECOVER (0.3s), then 3.5s cooldown. The telegraph is what makes it fair - flash/scale the sprite during it. Knockback: on hit, set `_knockback_vel = (pos - source).normalized() * 180`, decay with `move_toward(Vector2.ZERO, 900 * delta)` and add to movement. ### Hit feedback and death (non-negotiable) `take_damage(amount, source_pos, is_crit)` must: flash the sprite, spawn a floating damage number (bigger + colored on crit), spawn directional particles, apply knockback, show the health bar. Death: `GameManager.add_kill()`, `add_xp(xp_value)`, drop gold (rare health orb), particle burst, then disable before animating out: ```gdscript theme={null} set_physics_process(false) set_deferred("monitoring", false) set_deferred("monitorable", false) var tween := create_tween().set_parallel(true) tween.tween_property(self, "scale", scale * 1.5, 0.1) tween.tween_property(self, "modulate:a", 0.0, 0.1) tween.chain().tween_callback(queue_free) ``` The `set_deferred` pair matters: freeing an Area2D mid-physics-callback without disabling monitoring first throws errors. ## Spawner and wave data The spawner reads a per-wave config and spawns groups on an interval, always off-screen (650-900px from the player, clamped to arena bounds): ```gdscript theme={null} func _random_spawn_pos() -> Vector2: var angle := randf() * TAU var dist := randf_range(650.0, 900.0) var pos := GameManager.player_node.global_position + Vector2.from_angle(angle) * dist pos.x = clampf(pos.x, -ARENA_HALF_SIZE, ARENA_HALF_SIZE) pos.y = clampf(pos.y, -ARENA_HALF_SIZE, ARENA_HALF_SIZE) return pos ``` Each WaveConfig: `enemy_weights: Dictionary`, `spawn_interval`, `group_size`, `max_alive`, `elite_chance`, `boss: bool`, `hazards: int`, `duration`. Type selection is weighted random over the dictionary. Hand-tune 20 waves; the ramp that matters: | Wave | Types | Interval | Group | Max alive | Elite % | Boss | Duration | | - | - | - | - | - | - | - | - | | 1 | walker | 2.5s | 2 | 25 | 0% | no | 20s | | 3 | +runner | 2.0s | 4 | 45 | 0% | no | 20s | | 5 | +charger | 1.7s | 5 | 65 | 3% | no | 22s | | 8 | +tank +ranged | 1.3s | 8 | 100 | 6% | no | 22s | | 10 | all 6 | 1.1s | 10 | 120 | 8% | YES | 30s | | 15 | tank heavy | 0.75s | 15 | 190 | 13% | no | 28s | | 20 | max density | 0.45s | 22 | 250 | 20% | YES | 30s | Do NOT scale difficulty by HP alone. The ramp is spawn rate + group size + max alive + type diversity + elite chance + new mechanics at fixed waves. Bosses spawn 3s into their combat phase via a scene-tree timer. Arena hazards from wave 3+: spike traps (static) and fire pools (drift at 15-35px/s). Tick damage every 0.6s (6 + wave\*1.5) to enemies in radius, half damage to the player - positioning pressure for both sides. ## Elites `elite_system.gd` is a static RefCounted helper applied at spawn time with `elite_chance` probability. One of four modifiers, 3x XP: * FAST: speed x1.8, HP x1.3, lightened color * TANKY: HP x3, scale x1.3, contact damage x1.5, darkened * SPLITTING: HP x1.5, green; on death spawns 2 walker copies at 0.6x scale, 0.3x HP (use `call_deferred("add_child", copy)` - you are inside a physics callback) * VAMPIRIC: HP x2; heals 8% max HP every 3s Give elites a visible pulse tween so players can prioritize them. ## Two-track progression Track 1 - mid-wave level-ups: on level-up the tree pauses, 3 random stat upgrades from the pool are offered, each stackable to level 3. Also vacuum all pickups (`attract()` on the "pickups" group) as a reward beat. | Upgrade | Per level | Stat touched | | - | - | - | | Might | +15% damage | player\_damage\_mult | | Haste | +12% attack speed | player\_attack\_speed\_mult | | Swiftness | +20 speed | player\_speed | | Vitality | +15 max HP (and heal 15) | player\_max\_health | | Magnetism | +20 pickup range | player\_pickup\_range | | Armor | +1 flat reduction | player\_armor | | Regeneration | +0.5 HP/s | player\_regen | | Critical Eye | +5% crit | player\_crit\_chance | `get_random_choices(3)` filters out maxed upgrades, shuffles, takes 3. `apply_upgrade` bumps level and writes the stat straight onto GameManager. Armor applies as `maxi(1, amount - player_armor)` - always at least 1 damage. Track 2 - between-wave shop: 4 random items, gold-priced, 4 tiers (Common / Uncommon / Rare / Legendary). Tier odds shift with wave - by wave 16+: 15% Legendary / 30% Rare / 35% Uncommon / 20% Common; waves 1-5 have no Legendary at all. Prices scale `cost_base * (1.0 + wave * 0.12)`; reroll costs `2 + reroll_count + wave / 5` (escalates within a single shop visit). Items are either stat dictionaries applied to GameManager (`{"player_armor": 2}`) or weapon grants that call `player.add_or_upgrade_weapon(id)`. The interesting ones trade off: ```gdscript theme={null} _add("glass_cannon", "Glass Cannon", 2, 40, {"player_damage_mult": 0.35, "player_max_health": -25}, ["offense"]) _add("berserker_mask", "Berserker Mask", 2, 45, {"player_damage_mult": 0.25, "player_attack_speed_mult": 0.20, "player_armor": -3}, ["offense"]) ``` Do not skip the shop. Without a between-wave decision point the game is just "survive longer"; trade-off items are what create builds. ## Weapon evolution A base weapon evolves when the player owns it AND a specific catalyst upgrade is maxed (level 3). Check after every upgrade pick and shop purchase; emit `evolution_available` once per recipe: | Evolved | Base weapon | Catalyst | Effect | | - | - | - | - | | Piercing Barrage | Projectile | Multi Shot | pierces 4+, faster bullets | | Radiant Barrier | Orbital | Armor | 4 large orbitals + damage pulses | | Supernova | Holy Nova | Might | bigger AoE + burning ground DOT | Evolving replaces the node: `queue_free()` the old weapon, erase from the player's `_weapons` dict, instantiate the evolved script, screen flash + zoom pulse. DOT zones (Supernova) are a Polygon2D + tween loop: N tick callbacks at 0.5s intervals doing a group distance scan, then fade and free. Guard every tick with `is_instance_valid` - the zone can outlive enemies and vice versa. ## Characters Four picks before the run, each a starting weapon + stat override dictionary: * Sentinel: projectile, no overrides (baseline) * Berserker: projectile, damage\_mult 1.4, speed 240, max HP 80 * Warden: orbital, max HP 150, armor 3, attack\_speed 0.85 * Arcanist: nova, attack\_speed 1.25, damage\_mult 1.15, max HP 70 `GameManager.reset_run()` resets all stats to base, then applies `selected_character.stat_overrides` via `set(key, value)` and fills health to max. Character select is just 4 cards that set `selected_character` and load the arena. ## UI stack (all procedural, all CanvasLayer, all process\_mode ALWAYS) * HUD: health + dash bars top-left, wave counter + timer top-center, gold/kills/level top-right, full-width 6px XP bar at the bottom. * LevelUpUI (layer 20): dark overlay, 3 cards, gamepad focus. * ShopUI (layer 25): stats panel left, 4 tier-colored item cards, reroll + next-wave buttons, "SOLD" placeholders, live stat refresh after purchase. * PauseMenu / GameOverUI (layer 40): game over shows victory or death plus time / kills / level / wave, retry + menu. Retry = `get_tree().paused = false` THEN `reload_current_scene()`. Forgetting the unpause is the classic frozen-retry bug. ## Audio integration points Pooled AudioManager (16 global + 16 positional players, round-robin; all play methods null-safe so missing streams never crash). Pitch variance 5% global / 10% positional prevents machine-gun repetition. Hook: enemy hit + death (positional), pickup collect, level-up, shop purchase, weapon fire (-6dB, it fires constantly), music on combat start with fade. *** Source: [`library/skills/make-game/references/2d-survivors-progression.md`](https://github.com/SummerEngine/summer/blob/main/library/skills/make-game/references/2d-survivors-progression.md), rendered from `summer-engine@4.3.0` on npm. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.