Click fish to eat. Eat fish to gain XP. Gain XP to add levels. Leveling increases value gained from eating, but gets harder as level increases. Click pet to reset. CAUTION: In real life, eating fish COSTS coins.
Code ideas for a dear friend: Leveling and value multiplier. Coin scoring is moved to the pet. Coin-gain is based on the "value" of the collectible, multiplied by the pet's "value multiplier". CAUTION: This means that each pet nomming the collectible will add the whole, multiplied collectible "value" to the coin score: 2 pets with a 2.0 multiplier on a 2-point collectible = 2*2.0*2 = 8 coins added. The pet's "value multiplier" goes up a certain amount (0.15) with each level. XP-gain is equal to the "value" of the collectible. XP for next level is based on pet level, times a base amount (50), times the "value multiplier". To reach level 2, you need 1*1*50 = 50 XP. To reach level 3, you need 2*1.15*50 = 115 XP (so you need 65 XP to go from 2 to 3). To be level 4, you need 3*1.3*50 = 195 XP (195-115 = 80 XP to go from 3 to 4). This means the added XP required to level up keeps getting bigger, but XP-gain doesn't: eventually, leveling gets so hard, you'll want to replace your pet, or move on to an area with higher-value collectibles.