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

:root {
    --primary-color: #5e72e4;
    --primary-hover: #4c63d2;
    --secondary-color: #f7fafc;
    --text-primary: #2d3748;
    --text-secondary: #718096;
    --border-color: #e2e8f0;
    --success-color: #48bb78;
    --danger-color: #f56565;
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    color: var(--text-primary);
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: var(--shadow-lg);
    padding: 40px;
    max-width: 600px;
    width: 100%;
    animation: fadeIn 0.5s ease-in;
}

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

header {
    text-align: center;
    margin-bottom: 40px;
}

h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 10px;
    font-weight: 700;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.timer-display {
    position: relative;
    width: 280px;
    height: 280px;
    margin: 0 auto 40px;
}

.timer {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 4rem;
    font-weight: 300;
    color: var(--primary-color);
    font-variant-numeric: tabular-nums;
    letter-spacing: 0.05em;
    z-index: 2;
}

.progress-ring {
    position: absolute;
    top: 0;
    left: 0;
    transform: rotate(-90deg);
}

.progress-ring-bg {
    fill: none;
    stroke: var(--border-color);
    stroke-width: 8;
}

.progress-ring-circle {
    fill: none;
    stroke: var(--primary-color);
    stroke-width: 8;
    stroke-linecap: round;
    transition: stroke-dashoffset 0.5s ease;
}

.presets {
    display: flex;
    gap: 10px;
    justify-content: center;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

.preset-btn {
    background: var(--secondary-color);
    border: 2px solid var(--border-color);
    border-radius: 12px;
    padding: 10px 20px;
    font-size: 1rem;
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 500;
}

.preset-btn:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.preset-btn span {
    margin-left: 2px;
    font-size: 0.9rem;
}

.custom-input {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-bottom: 30px;
}

.custom-input input {
    width: 100px;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    font-size: 1.2rem;
    text-align: center;
    transition: border-color 0.3s ease;
}

.custom-input input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.custom-input span {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

.controls {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-bottom: 30px;
}

.control-btn {
    padding: 14px 32px;
    border: none;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    background: var(--secondary-color);
    color: var(--text-primary);
    box-shadow: var(--shadow-sm);
}

.control-btn:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.control-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.control-btn.primary {
    background: var(--primary-color);
    color: white;
}

.control-btn.primary:hover:not(:disabled) {
    background: var(--primary-hover);
}

.settings {
    display: flex;
    flex-direction: column;
    gap: 15px;
    padding: 20px;
    background: var(--secondary-color);
    border-radius: 12px;
    margin-bottom: 30px;
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: 10px;
    cursor: pointer;
    color: var(--text-primary);
    font-size: 1rem;
}

.checkbox-label input[type="checkbox"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

footer {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.language-selector {
    margin-bottom: 15px;
}

.language-selector select {
    padding: 8px 16px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background: white;
    cursor: pointer;
    transition: border-color 0.3s ease;
}

.language-selector select:focus {
    outline: none;
    border-color: var(--primary-color);
}

footer p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* レスポンシブデザイン */
@media (max-width: 640px) {
    .container {
        padding: 30px 20px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    .timer {
        font-size: 3rem;
    }
    
    .timer-display {
        width: 240px;
        height: 240px;
    }
    
    .progress-ring svg {
        width: 240px;
        height: 240px;
    }
    
    .progress-ring-bg,
    .progress-ring-circle {
        r: 110;
        cx: 120;
        cy: 120;
    }
    
    .presets {
        gap: 8px;
    }
    
    .preset-btn {
        padding: 8px 16px;
        font-size: 0.9rem;
    }
    
    .controls {
        flex-direction: column;
    }
    
    .control-btn {
        width: 100%;
    }
}

/* ダークモード対応（システム設定に従う） */
@media (prefers-color-scheme: dark) {
    :root {
        --secondary-color: #1a202c;
        --text-primary: #f7fafc;
        --text-secondary: #a0aec0;
        --border-color: #2d3748;
    }
    
    body {
        background: linear-gradient(135deg, #2d3748 0%, #1a202c 100%);
    }
    
    .container {
        background: #2d3748;
    }
    
    .custom-input input {
        background: #1a202c;
        color: var(--text-primary);
    }
    
    .control-btn {
        background: #1a202c;
        color: var(--text-primary);
    }
    
    .settings {
        background: #1a202c;
    }
    
    .language-selector select {
        background: #1a202c;
        color: var(--text-primary);
    }
    
    .preset-btn {
        background: #1a202c;
        color: var(--text-primary);
    }
}