:root {
    --bg-color: #f0f4f8;
    --text-color: #2d3748;
    --accent-color: #a0ced9;
    --circle-color: #c3e6f0;
    --circle-border: #81d4fa;
    --primary-btn: #64b5f6;
    --primary-btn-hover: #42a5f5;
    --white: #ffffff;
    --transition-slow: all 4s ease-in-out;
    --transition-med: all 2s ease-in-out;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    overflow: hidden;
    transition: background-color 2s ease;
}

body.bg-inhale {
    background-color: #e3f2fd;
}

body.bg-hold {
    background-color: #f3e5f5;
}

body.bg-exhale {
    background-color: #e8f5e9;
}

.app-container {
    text-align: center;
    max-width: 600px;
    width: 90%;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

header {
    animation: fadeInDown 1s ease-out;
}

.title {
    font-size: 3rem;
    font-weight: 600;
    color: #4a5568;
    letter-spacing: -1px;
    margin-bottom: 0.5rem;
}

.subtitle {
    font-size: 1.1rem;
    font-weight: 300;
    color: #718096;
}

.visualizer-area {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 3rem 0;
}

.circle-outer {
    position: relative;
    width: 300px;
    height: 300px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.circle {
    width: 100px;
    height: 100px;
    background: radial-gradient(circle, var(--circle-color) 0%, var(--accent-color) 100%);
    border-radius: 50%;
    box-shadow: 0 0 50px rgba(160, 206, 217, 0.5);
    transition: var(--transition-slow);
    z-index: 1;
}

.instruction {
    position: absolute;
    font-size: 1.5rem;
    font-weight: 400;
    color: #4a5568;
    z-index: 2;
    pointer-events: none;
    transition: opacity 0.5s ease;
}

.controls {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
}

.primary-button {
    padding: 1rem 2.5rem;
    font-size: 1.1rem;
    font-family: 'Inter', sans-serif;
    font-weight: 600;
    color: var(--white);
    background-color: var(--primary-btn);
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(100, 181, 246, 0.3);
}

.primary-button:hover {
    background-color: var(--primary-btn-hover);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(100, 181, 246, 0.4);
}

.primary-button:active {
    transform: translateY(0);
}

.timer {
    font-size: 1.2rem;
    font-weight: 300;
    color: #718096;
    font-variant-numeric: tabular-nums;
}

footer {
    font-size: 0.9rem;
    color: #a0aec0;
    font-weight: 300;
    margin-top: 1rem;
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Circle states */
.circle.inhale {
    transform: scale(2.5);
    background: radial-gradient(circle, #e1f5fe 0%, #81d4fa 100%);
    box-shadow: 0 0 80px rgba(129, 212, 250, 0.6);
}

.circle.hold {
    transform: scale(2.5);
    background: radial-gradient(circle, #f3e5f5 0%, #ce93d8 100%);
    box-shadow: 0 0 80px rgba(206, 147, 216, 0.6);
}

.circle.exhale {
    transform: scale(1);
    background: radial-gradient(circle, #e8f5e9 0%, #a5d6a7 100%);
    box-shadow: 0 0 80px rgba(165, 214, 167, 0.6);
}